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BIOCHEM LEC > PRE FI LEC 3: ENZYMES > Flashcards

PRE FI LEC 3: ENZYMES Flashcards

1
Q

the chemical reaction is triggered by the _______

A

enzyme

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2
Q

CHARACTERISTIC OF ENZYME
- each of them speeding up only one particular reaction or class of reactions
- E.g., The enzyme urease catalyzes only the hydrolysis of urea and not that other amides, even closely related ones.

A

EXTREME SPECIFIC

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3
Q

EXTREME SPECIFIC
- fix/specific
- can’t be adjust
- an enzyme will catalyze a particular reaction for only one substrate
- most restrictive of all specificities (not common)
- E.g., Catalase is an enzyme with absolute specificity for hydrogen peroxide (H2O2)

A. ABSOLUTE SPECIFICITY
B. STEREOCHEMICAL SPECIFICITY

A

ABSOLUTE SPECIFICITY

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4
Q

EXTREME SPECIFIC
-o an enzyme can distinguish between stereoisomers
o E.g., L-Amino-acid oxidase - catalyzes reactions of L-amino acids but not of D-amino acids

A. ABSOLUTE SPECIFICITY
B. STEREOCHEMICAL SPECIFICITY

A

STEREOCHEMICAL SPECIFICITY

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5
Q

CHARACTERISTIC OF ENZYME
- Increasing reaction rates by anywhere from 10^9 to 10^20 times
- E.g., Oxidation of Glucose

EXTREME SPECIFIC OR EXTREMELY EFFECTIVE?

A

EXTREMELY EFFECTIVE

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6
Q

EXTREMELY EFFECTIVE
o involves structurally similar compounds that have the same FUNCTIONAL GROUPS
o E.g., Carboxypeptidase: Cleaves amino acids one at a time from the carboxyl end of the peptide chain

A

GROUP SPECIFICITY

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7
Q

EXTREMELY EFFECTIVE
o involves a particular type of BOND irrespective of the structural features in the vicinity of the bond
o Considered most general of enzyme specificities
o E.g., Phosphatases: Hydrolyze phosphate–ester bonds in all types of phosphate esters
ex: peptidase = peptide bonds
hydrolases = hydrogen bonds

A

LINKAGE SPECIFICITY

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8
Q

ENZYME STRUCTURES
- composed only of protein (amino acid chains)
- protein portion consist of amino acids residues

A

SIMPLE ENZYMES

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9
Q

ENZYME STRUCTURES
- both protein and non-protein portions
Ex: HOLOENZYME

A

COMPLEX ENZYMES

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10
Q
  • protein portion of a CONJUGATED enzyme
  • cannot catalyze a reaction without a cofactor, nor can the cofactor function without apoenzyme
  • activator can either be inorganic IONS (metals) or or organic (COENZYMES)
A

APOENZYME

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11
Q

non-protein portion of a CONJUGATED enzyme

A

COFACTOR (ativator)

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12
Q

the biochemically active conjugated enzyme

A

HOLOENZYME

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13
Q

APOENZYME (protein portion, inactive) + COFACTOR (non-protein portion, activator) =

A

HOLOENZYME (whole enzyme, active)

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14
Q
  • Non-protein part of a conjugated enzyme
  • may be metallic ions: Ex. Zn2+, Mg2+, Mn2+, and Fe2+
  • non metallic ion cofactor: Ex . Cl-
  • inorganic ion cofactors derived from dietary minerals
  • may also be organic compounds
A

COFACTOR

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15
Q

Organic cofactors
Ex:
✔ Vitamin B – essential to the activity of many enzymes
✔ Heme – part of several oxidoreductases, part of hemoglobin

A

COENZYME

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16
Q
  • Compound on which the enzyme works and speeds up the reactions
  • binds to the enzyme’s surface (active site) while it undergoes the reaction
A

SUBSTRATE

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17
Q
  • a three-dimensional cavity of the enzyme with specific chemical properties to accommodate the substrate; place where SUBSTRATE BINDS TO ENZYME
  • usually a “CREVICE LIKE” location in the enzyme
  • relatively small part of an enzyme’s structure that is actually involved in catalysis
  • formed due to folding and bending of the protein
  • if the enzyme has coenzymes, they are located at the _____
  • some enzymes have more than one _____
A

ACTIVE SITE

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18
Q

ENZYME NOMENCLATURE
- suffix ____ identifies it as an enyzme

A

ASE

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19
Q

ENZYME NOMENCLATURE
- exception: the suffix ___ is still found in some digestive enzyme
ex: pepsin, trypsin, amylopsin

A

IN

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20
Q

ENZYME NOMENCLATURE
- type of reaction catalyzed by an enzyme is often used as ______
ex: OXIDASE: catalyze oxidation reaction
HYDROLASE: catalyze hydrolysis reaction

A

PREFIX

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21
Q

ENZYME NOMENCLATURE
- Identity of a ______ is often used in addition to the type of reaction
EX: Glucose oxidase succinate dehydrogenase, lactate dehydrogenase

A

SUBSTRATE

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22
Q

ENZYME CLASSIFICATION
- catalyze redox reactions
- requires a coenzyme that is either oxidized or reduced as the substrate in the reaction
- E.g., Lactate dehydrogenase is an oxidoreductase and
NAD+ is the coenzyme in this reaction.

A

OXIDOREDUCTASES

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23
Q

ENZYME CLASSIFICATION
- transfer of functional group

A

TRANSFERASES

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24
Q

ENZYME CLASSIFICATION
- removal of water to break hydrogen bond

A

HYDROLASEs

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25
Q

ENZYME CLASSIFICATION
- addition of a group to a double bond or removal of a group to form a double bond

A

LYASES

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26
Q

ENZYME CLASSIFICATION
- rearrangement of atoms

A

ISOMERASES

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27
Q

ENZYME CLASSIFICATION
- reactions involving bond formation coupled with ATP hydrolysis

A

LIGASES

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28
Q

SUBSTRATE BINDING MODULES
- Enzyme has a PRE -DETERMINED SHAPE for the active site
* Only substrate of SPECIFIC SHAPE can bind with active site

A

LOCK KEY MODEL

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29
Q

SUBSTRATE BINDING MODULES
- Substrate contact with enzyme will CHANGE THE SHAPE of the active site
- Allows SMALL CHANGE in space to accommodate substrate
(e.g., how a hand fits into a glove)

A

INDUCED FIT MODEL

30
Q

REGULATION OF ENZYMES
- regulators that INCREASE enzyme activity

A

ACTIVATORS

31
Q

REGULATION OF ENZYMES
- regulators that DECREASE enzyme activity

A

INHIBITORS

32
Q

REGULATION OF ENZYMES
- a substance that slows down or stops the normal catalytic function of an enzyme by binding to it

A

ENZYME INHIBITOR

33
Q

ENZYME INHIBITION
- COMPETE with the substrate for the same active site
- will have similar charge & shape with the substrate
- decreases enzyme activity by binding to the same active site as the substrate.
- binds reversibly to an enzyme active site and the inhibitor remains unchanged (no reaction occurs)
- the enzyme - inhibitor complex formation is via weak interactions (hydrogen bonds, etc.).
- can be reduced by simply increasing the concentration of the substrate
- decreases enzyme activity by binding to a site on an enzyme other than the active site.
- causes a change in the structure of the enzyme and prevents enzyme activity.
- increasing the concentration of substrate does not completely overcome inhibition.
examples: heavy metal ions Pb2+, Ag+, and Hg2+.
- inhibitor binds to the ACTIVE SITE
- NO REACTION
- directly blocks the active site

A

COMPETITIVE INHIBITION

34
Q

ENZYME INHIBITION
- DO NOT COMPETE with the substrate for the same active site
- binds to the enzyme at a location other than active site
- inhibitor binds to the ALLOSTERIC SITE
- NO REACTION
- changes the shape of the active site

A

NON-COMPETITIVE INHIBITION

35
Q

REVERSIBLE OR IRREVERSIBLE ENZYME INHIBITION
- the process of binding inhibitors to the enzyme through MONOVALENT INTERACTIONS, so that once removed, they allow the restoring of the enzyme function

A

REVERSIBLE ENZYME INHIBITION

36
Q

REVERSIBLE OR IRREVERSIBLE ENZYME INHIBITION
- binding of inhibitors to the enzyme through COVALENT INTERACTIONS, so that, their dissociation takes a long time
- PERMANENTLY REMOVING the enzyme action

A

IRREVERSIBLE ENZYME INHIBITION

37
Q

REVERSIBLE OR IRREVERSIBLE ENZYME INHIBITION
- bind to the enzyme through NON-COVALENT INTERACTIONS such as:
hydrogen bonds
hydrophobic interactions
ionic bonds

A

REVERSIBLE ENZYME INHIBITION

38
Q

REVERSIBLE OR IRREVERSIBLE ENZYME INHIBITION
- bind to the enzyme through COVALENT INTERACTIONS, which modify amino acids residues by reactive functional groups

A

IRREVERSIBLE ENZYME INHIBITION

39
Q

REVERSIBLE OR IRREVERSIBLE ENZYME INHIBITION
- enzyme inhibitor dissociates quickly

A

REVERSIBLE ENZYME INHIBITION

40
Q

REVERSIBLE OR IRREVERSIBLE ENZYME INHIBITION
- enzyme inhibitor dissociates very slowly

A

IRREVERSIBLE ENZYME INHIBITION

41
Q

REVERSIBLE OR IRREVERSIBLE ENZYME INHIBITION
- enzymatic action can be restored

A

REVERSIBLE ENZYME INHIBITION

42
Q

REVERSIBLE OR IRREVERSIBLE ENZYME INHIBITION
- it takes a long time to restore the enzymatic reaction

A

IRREVERSIBLE ENZYME INHIBITION

43
Q

REVERSIBLE OR IRREVERSIBLE ENZYME INHIBITION
- types: competitive, uncompetitive, non-competitive and mixed inhibition

A

REVERSIBLE ENZYME INHIBITION

44
Q

REVERSIBLE OR IRREVERSIBLE ENZYME INHIBITION
- occurs through the COVALENT INACTIVATION of the active site of the enzyme

A

IRREVERSIBLE ENZYME INHIBITION

45
Q

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

A

Enzyme Activity

46
Q

Higher temperature = higher kinetic energy = increase in number of reactant collisions, therefore there is higher activity
T OR F?

A

T

47
Q

temperature at which the rate
of enzyme catalyzed reaction is maximum

A

Optimum temperature

48
Q

Optimum temperature for human enzymes is_____(body temperature)

A

37ºC

49
Q

Increased temperature (high fever) leads to ________________________________

A

decreased enzyme activity

50
Q

Drastic changes in pH can result in denaturation of
proteins
T OR F?

A

T

51
Q

pH at which enzyme has maximum activity

A

Optimum pH

52
Q

Most enzymes have optimal activity in the pH range of

A

7.0 - 7.5

53
Q

Most enzymes have optimal activity in the pH range of 7.0 - 7.5
Exception:

A

Digestive enzymes

54
Q

Pepsin: Optimum pH

A

2.0

55
Q

Trypsin: Optimum pH

A

8.0

56
Q

at a constant enzyme concentration, the enzyme activity increases with increased substrate concentration.

T OR F?

A

T

57
Q

the concentration at which it reaches its maximum rate and all of the active sites are full

A

Substrate saturation

58
Q

Number of substrate molecules converted to product per second per enzyme molecule under conditions of optimum temperature
and pH

A

Turnover Number

59
Q

at a constant substrate concentration, enzyme activity increases with increase in enzyme concentration
T OR F?

A

T

60
Q

the greater the enzyme concentration, the lower the reaction rate.

T OR F?

A

F, the greater the enzyme concentration, the GREATER the reaction rate.

61
Q
  • Mechanism of regulation by production of enzymes in an INACTIVE FORMS
  • also known as pro-enzymes, are “turned on” at the
    appropriate time and place
    Example: proteolytic enzymes: Most digestive and
    blood-clotting enzymes are proteolytic enzymes:
    hydrolyze peptide bonds in proteins
    o Pepsinogen -> Pepsin, Fibrinogen -> Fibrin
A

ZYMOGENS

62
Q
  • a process in which activation or inhibition of the first reaction in a reaction sequence is controlled by a product of the reaction sequence
  • regulators of a particular allosteric enzyme may be:
  • products of entirely different pathways of reaction within the cell
  • compounds produced outside the cell (hormones)
A

Feedback Control

63
Q

PROPERTIES OF ALLOSTERIC ENZYMES
all allosteric enzymes have ______________
- composed of two or more protein chains

A

quaternary structure

64
Q

PROPERTIES OF ALLOSTERIC ENZYMES
enzymes have at least two binding sites:

A

substrate and regulator binding site
- active and regulatory binding sites are distinct from each other (located independent of each other)

65
Q

PROPERTIES OF ALLOSTERIC ENZYMES
Binding of molecules at the regulatory site causes
changes in the overall 3D structure of the enzyme
- Change in 3D structure of the enzyme = change in
_______

A

ENZYME ACTIVITY

66
Q

DRUGS THAT INHIBIT ENZYMES

A

✔ ACE INHIBITORS (ACE= Angiotensin Converting Enzyme)
✔ SULFA DRUGS
✔ PENICILLIN
✔ CIPROFLOXACIN

67
Q
  • Angiotensin II is an octapeptide hormone that increases blood pressure via constriction of blood vessels.
  • ACE converts Angiotensin I to angiotensin II in the blood.
  • ACE inhibitors BLOCK ACE REDUCTION and thus REDUCE BLOOD PRESSURE
A

ACE INHIBITORS (ACE= Angiotensin Converting Enzyme)

68
Q

example of a ACE inhibitor

A

Lisinopril

69
Q
  • derivatives of sulfanilamide (collectively _______)
  • as a sulfonamide antibiotic, sulfanilamide functions by competitively inhibiting enzymatic reactions involving para-aminobenzoic acid (PABA).
  • Mode of antibiotic activity:
    o Sulfanilamide is structurally similar to PABA (p aminobenzoic acid)
    o many bacteria need PABA to produce coenzyme, folic acid
    o Sulfanilamide is a COMPETITIVE INHIBITOR of enzymes responsible for CONVERTING PABA TO FOLIC ACID in bacteria
    o Folic acid deficiency retards bacterial growth and that eventually kills them
    o Sulfa drugs DON’T AFFECT HUMANS because we absorb folic acid from our diet
A

SULFA DRUGS

70
Q
  • accidently discovered by Alexander Fleming in 1928
  • several naturally occurring penicillins and numerous synthetic derivatives have been produced
  • selectively inhibits TRANSPEPTIDASE by covalent
    modification of serine residue
  • transpeptidase catalyzes the FORMATION OF PEPTIDE CROSS LINKS between polysaccharides strands in bacterial cell walls
A

PENICILLIN

71
Q

bactericidal action: INHIBITION OF THE ENZYMES
topoisomerase II (DNA gyrase) and topoisomerase IV
(both Type II topoisomerases), which are required for bacterial DNA replication, transcription, repair, and recombination

A

CIPROFLOXACIN

BIOCHEM LEC (10 decks)

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