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CHM040 - BIOMOLECULES > Chapter 4: Enzymes > Flashcards

Chapter 4: Enzymes Flashcards

1
Q

It is a rod-shaped bacterium originally discovered in a hot spring in Yellowstone National Park

A

Thermus aquaticus

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2
Q

Thermus aquaticus can survive at what temperature?

A

Temperatures between 50°C and 80°C

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3
Q

How do these organisms survive at these extreme temperatures that would cook the life-forms with which we are more familiar?

A
  • the structure of the enzyme that carry out all the work of the cells
  • held together by many more attractive forces
  • these proteins are stable and functional even at temperatures above the boiling point of water
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4
Q

Why was the T. aquaticus discovery important?

A

It is used in PCR, since Taq polymerase from T. aquaticus can withstand the temperature constraints of PCR.

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5
Q

What is PCR?

A
  • Polymerase Chain Reaction
  • it is a laboratory technique for rapidly producing (amplifying) millions to billions of copies of a specific segment of DNA
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6
Q

Steps in PCR:

A
  • Denaturation of helical DNA (94-96˚C)
  • Annealing (68˚C)
  • Elongation (72˚)
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7
Q

When was the Biological catalysis first recognized and described?

A

late 1700s

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8
Q

Biological catalysis was first recognized and described in studies on the ___

A

digestion of meat by secretions of the stomach

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9
Q

What examination takes place in the 1800s?

A

The conversion of starch to sugar by saliva and various plant extracts

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10
Q

In the 1850s, he concluded that fermentation of sugar into alcohol by yeast is catalyzed by “ferments”

A

Louis Pasteur

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11
Q

These ferments were inseparable from the structure of living yeast cells

A

Vitalism

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12
Q

In 1897, he discovered that yeast extracts could ferment sugar to alcohol, proving that fermentation was promoted by molecules that continued to function when removed from cells.

A

Eduard Buchner

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13
Q

He gave the name enzymes

A

Frederick W. Kuhne

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14
Q

Etymology of the word Enzyme (Greek)

A

“en” means inside
“zymos” means yeast

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15
Q

In 1926, he’s discovery was a breakthrough in early enzyme studies

A

James Sumner

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16
Q

What was the discovery of James Sumner that brought a breakthrough in early enzyme studies?

A

The isolation and crystallization of urease

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17
Q

What was Sumner found out and his assumption?

A
  • urease crystals consisted entirely of protein
  • all enzymes are proteins
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18
Q

In 1930s, they found out that crys pepsin, trypsin, and other digestive enzymes are also proteins

A

John Northrop and Moses Kunitz

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19
Q

What did J. B. S. Haldane wrote?

A

A treatise titled Enzymes

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20
Q

What was the remarkable suggestion of Haldane?

A

That weak bonding interactions between an enzyme and its substrate might be used to catalyze a reaction

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21
Q

Protein that is specialized to catalyze metabolic reactions

A

Enzyme (occasionally RNA; ribozymes)

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22
Q

Enzymes catalyze the reactions that break down food molecules to allow the cell to ___ ____

A

harvest energy

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23
Q

Enzymes, also catalyze the biosynthetic reactions that produce the great variety of ______ _____ for ____ ___

A

molecules required for cellular life

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24
Q

How important is the Enzymes to life?

A

About a quarter of the genes in the human genome encode enzymes

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25
Q

Proteins are highly effective catalysts because of their?

A

capacity to specifically bind a very wide range of molecules

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26
Q

How does enzymes catalyze reactions?

A

By stabilizing transition states

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27
Q

What is called to enzymes that requires an additional chemical component?

A

Cofactor

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28
Q

What are the inorganic ions that serves as cofactors for enzymes?

A
  • Fe2+/Fe3+
  • Mg2+
  • Mn2+
  • Cu2+
  • K+
  • Mo
  • Ni2+
  • Zn2+
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29
Q

A complex organic or metalloorganic molecule

A

Coenzyme

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30
Q

Components of Holoenzyme

A
  • Cofactor
  • Catalytic Site
  • Coenzyme
  • Apoenzyme
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31
Q

Why do apoenzymes need cofactors?

A

Cofactors provide additional chemically reactive functional groups besides those present in the amino acid side chains of apoenzymes

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32
Q

A coenzyme or metal ion that is very tightly or even covalently bound to the enzyme protein

A

Prosthetic group

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33
Q

A complete, catalytically active enzyme together with its bound coenzyme and/or metal ions

A

Holoenzyme

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34
Q

The protein part of such an enzyme

A

Apoenzyme or Apoprotein

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35
Q

NAD+

A

Nicotinamide adenine dinucleotide
(oxidized form)

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36
Q

NADH

A

reduced form NAD+

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37
Q

NADP+

A

Nicotinamide adenine dinucleotide phosphate
(oxidized form)

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38
Q

FAD

A

Flavin adenine dinucleotide
(oxidized form)

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39
Q

Finally, some enzyme proteins are modified covalently by ______, _____, and other processes

A
  • phosphorylation
  • glycosylation
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40
Q

Example of organic compound that show little tendency for reaction outside the cell

A

Glucose

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41
Q

Glucose is a ____ that can be stored _____ on the shelf with ___ ________

A
  • sugar
  • indefinitely
  • no deterioration
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42
Q

What is produce in most cell that quickly oxidized glucose?

A

carbon dioxide and water and releasing lots of energy

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43
Q

Glucose represents _____ _____

A

thermodynamic potentiality

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44
Q

What suffix identifies a substance as an enzyme?

A
  • ase
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45
Q

Examples of enzymes that ends with a suffix -ase

A
  • Urease
  • Sucrease
  • Lipase
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46
Q

What enzymes have a suffix -in in their names?

A

Digestive enzymes:
- Trypsin
- Chymotrypsin
- Pepsin

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47
Q

What are the prefixes denotes the type of reaction catalyzed by an enzyme?

A
  • Oxidase
  • Hydrolase
  • Carboxylase
  • Dehydrogenase
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48
Q

What type of reaction denotes the prefix oxidase?

A

Oxidation

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49
Q

What type of reaction denotes the prefix hydrolase?

A

Hydrolysis

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50
Q

What type of reaction denotes the prefix carboxylase?

A

Carboxylation

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51
Q

What type of reaction denotes the prefix dehydrogenase?

A

Dehydrogenation

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52
Q

The identity of the ____ is often noted in addition to the type of reaction

A

Substrate

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53
Q

Urease

A

catalyzes the hydrolysis of urea

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54
Q

Lactase

A

catalyzes the hydrolysis of lactose

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55
Q

What are six major classes of enzymes?

A
  1. Oxidoreductase
  2. Transferase
  3. Hydrolase
  4. Lyase
  5. Isomerase
  6. Ligase
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56
Q

Oxidoreductase

A

catalyzes an oxidation-reduction reaction

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57
Q

An oxidoreductase requires a _____ that is oxidized or reduced as the _____ is reduced or oxidized

A
  • coenzyme
  • substrate
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58
Q

It is an oxidation that increases the number of C—O bonds and/or decreases the number of C—H bonds

A

Oxidation reaction

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59
Q

Oxidation reaction:
Increases

A

The number of C—O bonds

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60
Q

Oxidation reaction:
Decreases

A

The number of C—H bonds

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61
Q

It is an reduction that decreases the number of C—O bonds and/or increases the number of C—H bonds

A

Reduction reaction

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62
Q

Reduction reaction:
Increases

A

The number of C—H bonds

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63
Q

Reduction reaction:
Decreases

A

The number of C—O bonds

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64
Q

How can the enzymatic browning of apple slowed or prevented?

A
  1. Cold water
  2. Refrigeration
  3. Boiling (denaure)
  4. Lemin Juice (acidic)
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65
Q

Transferase

A

catalyzes the transfer of a functional group from one molecule to another

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66
Q

Two major subtypes of Transferase

A
  1. Transaminase
  2. Kinases
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67
Q

It is the transfer of an amino group from one molecule to another

A

Transaminase

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68
Q
  • transfer of a phosphate group from adenosine triphosphate (ATP)
  • play a major role in energy harvesting processes involving ATP
A

Kinases

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69
Q

a product containing an additional
phosphate group

A

Phosphorylated product

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70
Q

Hydrolase

A

catalyzes a hydrolysis reaction in which the addition of a water molecule to a bond causes the bond to break

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71
Q

Why does the gelatin will not gel if fresh fruits is added?

A

because these fruits contain a protease (a hydrolase) that catalyzes the hydrolysis of peptide (amide) linkages in gelatin preventing the hydrogel from forming

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72
Q

Why does the gelatin gels when canned fruits is added?

A

The protease present is deactivated when the pineapple was cooked prior to packaging

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73
Q

Lyase

A

catalyzes the addition of a group to a double bond or the removal of a group to form a double bond in a manner that does not involve hydrolysis or oxidation

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74
Q

Isomerase

A

catalyzes the isomerization (rearrangement of atoms) of a substrate in a reaction, converting it into a molecule isomeric with itself

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75
Q

Ligase

A

catalyzes the bonding together of two molecules into one with the participation of ATP

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76
Q

Subclasses of Oxidoreductases

A
  • Oxidases
  • Reductases
  • Dehydrogenases
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77
Q

Type of reaction catalyzed by the subclass of Oxidoreductases:
Oxidases

A

oxidation of a substrate

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78
Q

Type of reaction catalyzed by the subclass of Oxidoreductases:
Reductases

A

reduction of a substrate

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79
Q

Type of reaction catalyzed by the subclass of Oxidoreductases:
Dehydrogenases

A

introduction of double bond (oxidation) by formal removal of two H atoms from a substrate, with one H being accepted by a coenzyme

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80
Q

Subclasses of Tranferases

A
  • Transaminases
  • Kinases
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81
Q

Type of reaction catalyzed by the subclass of Tranferases:
Transaminases

A

transfer of an amino acid between substrates

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82
Q

Type of reaction catalyzed by the subclass of Tranferases:
Kinases

A

transfer of a phosphate group between substrates

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83
Q

Subclasses of Hydrolases

A
  • Lipases
  • Proteases
  • Nucleases
  • Carbohydrases
  • Phosphatases
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84
Q

Type of reaction catalyzed by the subclass of Hydrolases:
Lipases

A

hydrolysis of ester linkages in lipids

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85
Q

Type of reaction catalyzed by the subclass of Hydrolases:
Proteases

A

hydrolysis of amide linkages in proteins

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86
Q

Type of reaction catalyzed by the subclass of Hydrolases:
Nucleases

A

hydrolysis of sugar-phosphate ester bonds in nucleic acids

87
Q

Type of reaction catalyzed by the subclass of Hydrolases:
Carbohydrases

A

hydrolysis of glycosidic nonds in carbohydrates

88
Q

Type of reaction catalyzed by the subclass of Hydrolases:
Phosphatases

A

hydrolysis of phosphate-ester bonds

89
Q

Subclasses of Lyases

A
  • Dehydratases
  • Decarboxylases
  • Deaminases
  • Hydratases
90
Q

Type of reaction catalyzed by the subclass of Lyases:
Dehydratases

A

removal of H2O from a substrate

91
Q

Type of reaction catalyzed by the subclass of Lyases:
Decarboxylases

A

removal of CO2 from a substrate

92
Q

Type of reaction catalyzed by the subclass of Lyases:
Deaminases

A

removal of NH3 from a substrate

93
Q

Type of reaction catalyzed by the subclass of Lyases:
Hydratases

A

addition of H2O to a substrate

94
Q

Subclasses of Isomerases

A
  • Racemases
  • Mutases
95
Q

Type of reaction catalyzed by the subclass of Isomerases:
Racemases

A

conversion of D isomer to L isomer, or vice versa

96
Q

Type of reaction catalyzed by the subclass of Isomerases:
Mutases

A

transfer of a functional group from one position to another in the same molecule

97
Q

Subclasses of Ligases

A
  • Synthetase
  • Carboxylases
98
Q

Type of reaction catalyzed by the subclass of Ligases:
Synthetases

A

formation of a new bond between two substrates, with participation of ATP

99
Q

Type of reaction catalyzed by the subclass of Ligases:
Carboxylases

A

formation of a new bond between a substrate and CO2, with participation of ATP

100
Q

A thermodynamic property that is a measure of useful energy, or the energy that is capable of doing work

A

Gibbs Free Energy (G)

101
Q

Two thermodynamic properties of how enzymes operate

A
  1. the free-energy difference (∆G) between the products and reactants
  2. the energy required to initiate the conversion of reactants into products (Ea)
102
Q

The free-energy change provides information about the ______ but NOT the ____ of a reaction

A
  • spontaneity
  • rate
103
Q

The free-energy change of a reaction (∆G) tells us if the reaction can take place spontaneously:

A
  1. A reaction can take place spontaneously; (∆G<0), ∆G is negative
  2. A system is at equilibrium and no net change can take place if ∆G is zero (∆G=0)
  3. A reaction cannot take place spontaneously; (∆G>0), ∆G is positive. An input of free energy is required to drive such a reaction
  4. The ∆G of a reaction is independent of the molecular mechanism of the transformation
  5. The rate of a reaction depends on the free energy of activation (∆G‡), which is largely unrelated to the ∆G of the reaction
104
Q

A reaction that can release energy

A

Exergonic

105
Q

A reaction that requires energy

A

Endergonic

106
Q

Endergonic Reactions

A
  • Reactio is not spontaneous
  • Energy is absorbed
  • ∆G>0
107
Q

Exergonic Reactions

A
  • Reaction is spontaneous
  • Energy is released
  • ∆G<0
108
Q

How does an enzyme speed up a chemical reaction?

A
  • by lowering the activation energy of the reaction
  • The energy difference between reactant (substrate) and product is not changed. It is only the activation energy that is reduced
109
Q

Enzymes alter only the ____ ___and not the ____ _______

A
  • reaction rate
  • reaction equilibrium
110
Q

X‡ denotes the transition state:

A
  • transitory molecular structure that is no longer the substrate but is not yet the product
  • the least-stable and most-seldom occupied species along the reaction pathway because it is the one with the highest free energy
111
Q

It is the difference in free energy between the transition state and the substrate

A

Gibbs free energy of activition or activation energy (∆G‡)

112
Q

What is the first step in enzymatic catalysis?

A

The formation of an enzyme-substrate complex

113
Q

Enzymes bind to and then alter the structure of the substrate to _____ the ______ of the ______ ____

A

promote the formation of the transition state

114
Q

What is the evidence for the existence of an enzyme–substrate complex?

A
  1. At constant concentration of enzyme, the reaction rate increases with increasing substrate concentration until a maximal velocity is reached
  2. The spectroscopic characteristics of many enzymes and substrates change on the formation of an ES complex
  3. X-ray crystallography
115
Q

Common features of the active sites of enzymes

A
  1. The active site is a three dimensional cleft, or crevice, formed by groups that come from different parts of the amino acid sequence
  2. The active site takes up a small part of the total volume of an enzyme
  3. Active sites are unique microenvironments
  4. Substrates are bound to enzymes by multiple weak attractions
  5. The specificity of binding depends on the precisely defined arrangement of atoms in an active site
116
Q

Models of Enzyme Action

A
  • Lock-and-key model
  • Induced fit model
117
Q

Only a substrate whose shape and chemical nature are complementary to those of the active site can interact with the enzyme

A

lock-and-key model

118
Q

The enzyme active site, although not exactly complementary in shape to that of the substrate, is felxible enough that it can adapt to the shape of the substrate

A

Induced fit model

119
Q

The _____ ____ between enzyme and substrate is important for catalysis

A

binding energy

120
Q

What is the binding energy?

A

Free energy released in binding

121
Q

The full complement of ____ ______ is formed only when the _____ is converted into the _____ ___

A
  • weak interactions
  • substrate
  • transition state
122
Q

A state in which the substrate is in an energetically unstable intermediate form, having features of both the substrate and the product

A

Transition state

123
Q

What kinds of transition state changes might occur in the substrate that would make a reaction proceed more rapidly?

A
  1. The enzyme might put “stress” on a bond and thereby promote bond breakage
  2. An enzyme may facilitate a reaction by bringing two reactants close to one another and in the proper orientation for reaction to occur
  3. The active site of an enzyme may modify the pH of the microenvironment surrounding the substrate
124
Q

It is the extent to which an enzyme’s activity is restricted to a specific substrate, a specific group of substrates, a specific type of chemical bond, or a specific type of chemical reaction

A

Enzyme specificity

125
Q

The degree of enzyme specificity is determined by the ____ ___

A

active site

126
Q

Types of Specificity

A
  1. Absolute specificity
  2. Group Specificity
  3. Linkage Specificity
  4. Stereochemical Specificity
127
Q

Absolute Specificity

A
  • the enzyme will catalyze only one reaction
128
Q

Example of Absolute specificity

A
  • Aminoacyl tRNA synthetases
  • Catalase
129
Q

Group Specificity

A

the enzyme will act only on molecules that have a specific functional group, such as hydroxyl, amino, or phosphate groups

130
Q

Example of Group specificity

A
  • Carboxypeptidase
  • Hexokinase
131
Q

Linkage Specificity

A
  • the enzyme will act on a particular type of chemical bond, irrespective of the rest of the molecular structure
  • is the most general of the common specificities
132
Q

Example of Linkage specificity

A
  • Phosphatases hydrolyze phosphate-ester
  • Poteases hydrolyze peptide bonds
133
Q

Stereochemical Specificity

A

the enzyme will act on a particular stereoisomer

134
Q

It is a measure of the rate at which an enzyme converts substrate to products in a biochemical reaction

A

Enzyme activity

135
Q

Factors that affect enzyme activity

A
  1. Temperature
  2. pH
  3. Substate concentration
  4. Enzyme concentration
136
Q

It is a measure of the kinetic energy (energy of motion) of molecules

A

Temperature

137
Q

At higher temperatures
molecules are moving _____
and ______ more ______

A
  • faster
  • colliding more frequently
138
Q

What is the optimum temperature for human enzymes?

A

37°C (normal body temperature)

139
Q

If a person has a fever, the body temperature exceeds to ____ can be in a life-threatening situation because it can initiate _____ ______

A
  • 40°C
  • enzyme denaturation
140
Q
  • it can destroy bacterial enzyme with its high-temperature and high pressure
  • it is used to sterilize medical instruments and laundry (in hospital)
A

Autoclaves

141
Q

How can Autoclaves kill bacterial enzymes?

A

Super-heated steam is used to produce a temperature sufficient to denature bacterial enzymes

142
Q

It is an equipment that sterilized instruments by dry heat (160°C) applied for at least 2 hours (h)

A

Dry air oven

143
Q

How does autoclave works?

A
  • works on the principle of the pressure cooker
  • air is pumped out of the chamber, and steam under pressure is pumped into the chamber until a pressure of 2 atmospheres (atm) is achieved
144
Q

The atmospheric pressure is greater than the vapor pressure

A

The water will not boil

145
Q

The atmospheric pressure is equal to the vapor pressure

A

The water starts to boil

146
Q

Atmospheric pressure alters the boiling point of water:
20,000 feet (6,000 meters)

A

Water boils at about 175°F (79°C)

147
Q

Atmospheric pressure alters the boiling point of water:
10,000 feet (3,000 meters)

A

Water boils at about 194°F (90°C)

148
Q

Atmospheric pressure alters the boiling point of water:
6,000 feet (1,800 meters)

A

Water boils at about 200°F (93°C)

149
Q

Atmospheric pressure alters the boiling point of water:
Sea level

A

Water boils at about 212°F (100°C)

150
Q

It is the pH at which an enzyme exhibits maximum activity

A

Optimum pH

151
Q

Small changes in pH (less than one unit) can result in _____ ______ and subsequent loss of catalytic activity

A

enzyme denaturation

152
Q

It helps maintain the optimum pH for an enzyme

A

Biochemical buffers

153
Q

Physiological pH range

A

7.0-7.5

154
Q

Pepsin, which is active in the stomach, functions best at ____

A

pH 2.0

155
Q

Trypsin, which operates in the small intestine, functions best at ______

A

pH 8.0

156
Q

Stomach and duodenal ulcers were thought to be due to ___

A
  • excess stomach acid
  • emotional stress
  • spicy food
157
Q

A clinical pathologist who had
examined many stomach biopsy specimens

A

J. Robin Warren

158
Q

What did J. Robin Warren noticed in examining many stomach biopsy specimens?

A

Noticed a parallel between the severity of the inflammation and
the number of bacteria present

159
Q

Who was the trainee doctor that Warren met in 1981?

A

Barry James Marshall

160
Q

Marshall was unsuccessful in developing an animal model, so he decided to _____ ____ ____

A

experiments upon himself

161
Q

absence of hydrochloric acid in the gastric secretions

A

Achlorhydria

162
Q

What did Marshall and Warren discover after their experiment?

A

H. pylori (Helicobacter pylori), a bacterium that causes stomach ulcer and not stress and lifestyle

163
Q

neutralizes gastric acid in the stomach

A

ammonia

164
Q

The urease itself is protected from _____ by its complex ___ ____

A
  • denaturation
  • quaternary structure
165
Q
  • called “suicide bags” (Christian de Duve, 1956)
  • they are membrane-bound vesicles containing about fifty different kinds of hydrolases that degrade large biological molecules into small molecules
A

Lysosomes

166
Q

What would be the result if the hydrolytic enzymes of the lysosome were accidentally released into the cytoplasm of the cell?

A
  • destruction of cellular molecules
  • death of the cell
167
Q

Lysosomal enzymes function optimally at _____

A

acid pH 4.8

168
Q

Enzyme-catalyzed reaction must occur in two stages:

A
  1. formation of an enzyme-substrate complex
  2. Conversion of substrate into product and release of the product and enzyme
169
Q

It is the region of the enzyme that specifically binds the substrate andcatalyzes the reaction

A

Active site

170
Q

It is dependent on the amount of enzyme that is available

A

Reaction rate

171
Q

It is the number of substrate molecules transformed per minute by one molecule of enzyme under optimum conditions of temperature, pH, and saturation

A

Turnover number

172
Q

The concentration of substrate
in a reaction is much _____ than that of the enzyme

A

higher

173
Q

It is a microorganism that thrives in extreme environments

A

Extremophile

174
Q

Extremophile environments

A
  • Hydrothermal areas of Yelllowstone National Park
  • Hydrothermal vents on the ocean floor (temperatures and pressure are extemely high)
175
Q

Microorganims that shows optimal growth at pH levels of 3.0 or below

A

Acidophiles

176
Q

An extremophiles that shows optimal growth at pH levels of 9.0 or above

A

Alkaliphiles

177
Q

An extremophiles that thrives in high salinity, a salinity that exceeds 0.2 M NaCl needed for growth

A

Halophiles

178
Q

Organims that can thrive at a temperature between 80°C and 121°C

A

Hyperthermophiles

179
Q

Organims that can thrive at a high hydrostatic pressure

A

Piezophiles

180
Q

Organims that can thrive at an extremely dry conditions

A

Xerophiles

181
Q

Organims that can thrive at a
temperature of 15°C or lower

A

Cryophiles

182
Q
  • enzyme present in extremophiles
  • a microbial enzyme active at conditions that would inactivate human enzymes as well as enzymes present in other types of higher organisms
A

Extremozymes

183
Q

Extremozymes have characteristics that have been found to be useful

A

can function in hot water and cold water wash (adapted)

184
Q

The development of commercially useful enzymes using extremophile sources involves the following general approach:

A
  1. Samples containing the extremophile are gathered from the extreme environment where it is found
  2. DNA material is extracted from the extremophile and processed
  3. Macroscopic amounts of the DNA are produced using the polymerase chain reaction
  4. The macroscopic amount of DNA is analyzed to identify the genes present that are involved in extremozyme production
  5. Genetic engineering techniques are used to insert the extremozyme gene into bacteria, which then produce the extremozyme
  6. The process is then commercialized
185
Q

Main reason why there is a necessity for the regulation of enzyme activity witin a cell

A

due to energy conservation (If the cell runs out of chemical energy, it will die)

186
Q

Many mechanisms exist by which enzymes within a cell can be “turned on”

A
  1. feedback control associated with allosteric enzymes,
  2. proteolytic enzymes and proenzymes/zymogens, and
  3. covalent modification
187
Q

Characteristics of allosteric enzymes:

A
  1. allosteric enzymes have quaternary structure
  2. have two kinds of binding sites
  3. two binding sites are distinct from each other in both location and shape
  4. Binding of a molecule at the regulatory site causes changes in the overall three-dimensional structure of the enzyme
188
Q

Two kinds of binding site

A
  • Substrate (active)
  • Regulators (regulatory)
189
Q

Structure of allosteric enzymes

A

Quaternary structure

190
Q

Two different sites of attachment in the allosteric enzymes

A
  • active site
  • effector binding site
191
Q
  • inactive form of enzyme
  • converted by proteolysis to the active form when it has reached the site of its activity
A

Proenzyme or zymogen

192
Q

hydrolysis of the protein

A

Proteolysis

193
Q

Example of proteolytic enzymes

A

most digestice and blood-clotting enzymes

194
Q

It is a process in which enzyme activity is altered by covalently modifying the structure of the enzyme through attachment of a chemical group to or removal of a chemical group from a particular amino acid within the enzyme’s structure

A

Covalent modification

195
Q

Most common type of protein modification

A
  • Phosphorylation (by protein kinases)
  • Dephosphorylation (by phosphatases)
196
Q

Example of the active phosphorylated version of the enzyme

A

triacylglycerol lipase

197
Q

Example of the active dephosphorylated version of the enzyme

A

glycogen synthase

198
Q

chemicals that can bind to enzymes and either eliminate or drastically reduce their catalytic ability

A

Enzyme inhibitors

199
Q

Example of Enzyme inhibitors

A

Arsenic and Penicilin

200
Q

It binds to the thiol groups of cysteine amino acids in the proteins, interfering with the formation of disulfide bonds needed to stabilize the tertiary structure of enzymes

A

Arsenic

201
Q

It inhibits several enzymes that are involved in the synthesis of bacterial cell walls

A

Penicillin

202
Q

Three (3) modes of inhibition:

A
  1. irreversible inhibition
  2. reversible competitive inhibition
  3. reversible noncompetitive inhibition
203
Q
  • do not have structure similar to that of the enzymes normal substrate
  • bind very tightly
  • binding of the inhibitor to one of the R groups of an amino acid in the active site
  • enzyme-substrate complex cannot form
  • may interfere with the catalytic groups of the active site
A

Irreversible Enzyme Inhibitors

204
Q

Irreverisble inhibitors include

A
  • venom
  • nerve gases
205
Q

Two types of Reversible enzyme inhibitors

A
  1. Reversible competitive inhibitors
  2. Reversible noncompetitive inhibitors
206
Q
  • often referred to as structural analogs
  • competitive, inhibitor and the substrate compete for binding to the enzyme active site
  • the degree of inhibition depends on their relative concentrations
A

Reversible competitive inhibitors

207
Q

The formation of an enzyme–competitive inhibitor complex is a _______ process because it is _____ by ____ _____

A
  • reversible
  • maintained by weak interactions
208
Q

How can the competitive inhibition be reduced?

A

by simply increasing the concentration of the substrate

209
Q
  • a molecule that decreases enzyme activity by binding to a site on an enzyme other than the
    active site
  • the inhibitor causes a change in the structure of the enzyme sufficient to prevent the catalytic groups at the active site from properly
A

Reversible noncompetitive inhibitors

210
Q

Examples of noncompetitive inhibitors

A

Heavy metal ions:
- Pb2+
- Ag+
- Hg2+

211
Q

Binding sites for these ions

A

Sulfhydryl (-SH; also called as thiol)

212
Q

What enzymes are serine proteses?

A

Pancreatic Serine Proteases
Chymotrypsin
Trypsin
Elastase

213
Q

Why are these enzymes called serine proteases?

A

because they have the amino acid serine in the catalytic region of the active site that is essential for hydrolysis of the peptide bond

CHM040 - BIOMOLECULES (4 decks)

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