Enzymology Flashcards
(192 cards)
1
Q
The molecules that enzymes act upon
A
Substrate
2
Q
Enzymes convert substrates into
A
Products
3
Q
______ depend upon enzymes to catalyze individual steps
A
Metabolic Pathways
4
Q
Almost all enzymes are
A
Proteins
5
Q
Enzymes follow the physical and chemical reactions of proteins. Notable exceptions include
A
Ribosomal RNAs and a handful of RNA molecules (Ribozymes)
5
Q
Enzymes are
A
Heat-labile and Water-soluble
6
Q
Enzymes can be precipitated by
A
Protein Precipitating Reagent
7
Q
Enzymes contain how much percent of nitrogen?
A
16%
8
Q
Enzymes that uses its first description in the earliest days of Biochemistry
A
Pepsin, Trypsin, Amylase
9
Q
Enzymes that remove hydrogen atoms
A
Dehydrogenases
10
Q
Enzymes that hydrolyze proteins
A
Proteases
11
Q
Enzymes that catalyze the rearrangements in configuration
A
Isomerases
12
Q
6 classes of enzymes according to IUBMB
A
Oxidoreductases, Transferases, Isomerases, Hydrolases, Lyases, Ligases
13
Q
Classification of enzyme that transfers hydrogen or adds oxygen
A
Oxidoreductases
14
Q
Oxidoreductases catalyze oxidation of one substrate while
A
Simultaneously reduces another substrate or Co-enzyme
15
Q
Examples of oxidoreductases
A
Lactate dehydrogenase, Glucose-6-phosphate dehydrogenase, Succinate dehydrogenase
16
Q
Classification of enzyme that transfers groups other than hydrogen
A
Transferases
17
Q
Examples of transferases
A
Hexokinase, Aminotransferases
18
Q
This type of enzymes can hydrolyze ester, ether, peptide, or glycosidic bonds by adding water and then breaking the bond
A
Hydrolases
19
Q
Examples of Hydrolases
A
Amylase, Maltase, Lactase, Lipase, Sucrose, Proteases, Acetyl Choline Esterase, Trypsin
20
Q
All digestive enzymes are
A
Hydrolases
21
Q
Classification of enzymes that cleaves without adding water
A
Lyases
22
Q
These enzymes can remove groups from substrates or break bonds by mechanisms other than hydrolases
A
Lyases
23
Q
Examples of lyases
A
Aldolase, HMG CoA lyase, ATP citrate lyase
24
Compound with same number of atoms rearranged
Isomers
25
Intramolecular transfers
Isomerases
26
The enzymes can produce optical, geometric or positional isomers of substrates
Isomerases
27
Examples of isomerases
Racemases, Epimerases, cis-trans isomerases
28
Classification of ATP dependent condensation of molecules
Ligases
29
These enzymes link 2 substrates together, usually with the simultaneous hydrolysis of ATP
Ligases
30
Meaning of the latin word Ligare
To bind
31
Examples of ligases
Acetyl CoA Carboxylase, Glutamine synthetase, PRPP synthetase
32
These types of enzymes are ATP-dependent which belong to ligases
Synthetase
33
Examples of Synthetase
Carbamoyl phosphate synthetase, Arginine succinate synthetase, PRPP Synthetase, Glutamine synthetase
34
Enzyme that do not require ATP directly
Synthase
35
Enzymes that belong to other classes other than ligase
Synthase
36
Examples of synthase
Glycogen synthase, ALA synthase
37
The deficient enzyme in Phenylketonuria
Phenylalanine hydroxylase
38
Phenylalanine is converted into _______ without phenylalanine hydroxylases, this accumulates that results to metabolic derangement
Tyrosine
39
Lactose is not digested at a normal rate and accumulates in the gut where it is metabolized by bacteria
Lactase deficiency
40
Emphysema results from an inherited deficiency of _____ an enzyme that inhibits elastase action in the lungs
a1-antitrypsin
41
____ is a serine protease found in neutrophils that utilize the enzyme to destroy inhaled organisms in the air
Elastase
42
At times, elastase may escape from the _____ and then the protease beings to destroy the lung cells
Neutrophil
43
The circulating ______ blocks the action of elastases and protects the lung from damage
protein cx1-antitrypsin
44
Cigarette smoke contains ____that will destroy a key ____ residue in a1-antitrypsin and destroy a1-antitrypsin activity
oxidizing agents, methionine
45
Complex enzymes contain a non-protein part called the
Prosthetic group
46
The prosthetic group is also called the
Co-enzyme
47
The co-enzyme is
heat stable
48
The apoenzyme is
heat-labile
48
The protein part of the enzyme is called the
Apozyme
49
The apoenzyme and co-factor combined together is called the
Holo-enzyme
50
This is essential for the biological activity of the enzyme
Co-enzyme
51
Co-enzyme is a ______ organic substance
low molecular weight
52
Generally, co-enzymes combine loosely with the
Enzyme molecule
53
The enzyme and co-enzyme can easily be separated by
Dialysis
54
Inside the body, when the reaction is completed, the co-enzyme is ________ from the apo-enzyme and can bind to another enzyme molecule
Released
55
One molecule of the co-enzyme is able to convert a large number of
Substrate molecules
56
Most of the co-enzymes are derivatives of
Vitamin B complex group of substances
57
2 groups of co-enzymes
(1) 1st group - donates and accepts Hydrogen atoms/electrons, (2) 2nd group - transfers groups other than Hydrogen
58
Group of co-enzymes that take part in reactions catalyzed by oxidoreductases by donating or accepting H atoms/electrons
First group
59
In the first group of co-enzymes, the change occurring in the substrate is ______ by the co-enzymes
counter-balanced
60
Where counter balancing by co-enzyme occurs it can be considered as
Co-substrates or secondary substrates
61
Examples of 1st group co-enzymes
NADP-NADPH; FAD-FADH2, FMN-FMNH2
62
These group of co-enzymes take part in reactions transferring groups other than hydrogen
2nd group of co-enzymes
63
In 2nd group of co-enzymes, a particular group or radical is ______ from the substrate to another substrate
transferred
64
(2nd group of co-enzyme) what group is transferred in the co enzyme thiamine pyrophosphate (TPP)?
hydroxy ethyl
65
(2nd group of co-enzyme) what group is transferred in the co enzyme pyridoxal phosphate (PLP)
amino group
66
(2nd group of co-enzyme) what group is transferred in the co enzyme biotin?
carbon dioxide
67
(2nd group of co-enzyme) what group is transferred in the co enzyme coenzyme-A (Co-A)
acyl groups
68
(2nd group of co-enzyme) what group is transferred in the co enzyme tetra hydrofolate (Fh4)
one carbon group
69
(2nd group of co-enzyme) what group is transferred in the co enzyme adenosine triphosphate (ATP)
phosphate
70
Considered as the energy currency in the body
ATP
71
in the ATP molecule, the ___ and ___ bonds are 'high energy' bonds
2nd; 3rd
72
During oxidation of food stuff, energy is released, a part of which is stored as ________ in the form ATP
chemical energy
73
These are enzymes which require certain metal ions for their activity
metallo-enzymes
74
What metal is contained in carbonic anhydrase, carboxy peptidase, alcohol dehydrogenase?
zinc
75
What metal is contained in hexokinase, phospho fructo kinase, enolase, glucose-6-phosphatase?
magnesium
76
What metal is contained in phospho gluco mutase, hexokinase, enolase, glycosyl transferases?
manganese
77
What metal is contained in tyrosinase, cytochrome oxidase, lysyl oxidase, superoxide dismutase?
copper
78
What metal is contained in cytochrome oxidase, catalase, peroxidase, xanthine oxidase?
iron
79
What metal is contained in lecithinase and lipase?
calcium
80
What metal is contained in xanthine oxidase?
molybdenum
81
Metal presence in enzymes can _____ activity
enhance
82
What do you call the enzymes that have enhanced activity when metal ions are added?
ion-activated enzymes
83
What are the mode of actions of enzymes?
lowering of activation energy, acid base catalysis, substrate strain, serine proteases, covalent catalysis, entropy effect
84
Enzymes lowers the
energy of activation
85
This is defined as the energy required to convert all molecules of a reacting substance from the ground state to the transition state
activation energy
86
Many acid-base catalysis reactions involve
histidine
87
why is histidine usually involved in acid-base catalysis?
because it's pH is close to 7
88
Having a pH of almost 7 allow for
acting as both acid and base
89
this helps histidine in acting as either an acid or base
ribonuclease
90
Binding of a substrate to a performed site on the enzyme can induce ____ in the substrate
strain
91
in the presence of substrate strain, the energy level of the substrate is
raised
92
A combination of substrate strain and acid base catalysis is seen in the action of
lysozome
93
enzymes that cleave peptide bonds in proteins
serine proteases
94
examples of serine proteases
chymotrypsin, trypsin, clotting factors
95
in this mode of action, this involves the substrate forming a transient covalent bond with residues in the enzyme active site or with a cofactor.
covalent catalysis
96
An additional covalent intermediate to the reaction in covalent catalysis helps to _____ the energy of later transition states of the reaction
reduce
97
in this mode of action, enzymes enhance reaction rates by decreasing entropy
entropy effect
98
In entropy effect, this reduces disorder by ______ substrates for reaction
orienting
99
a product substrate orientation theory that is also the enzyme-substrate complex theory
michaelis-menten theory
100
in michaelis-menten theory, the enzyme and substrate combine to form the
enzyme-substrate (ES) complex
101
in michaelis-menten theory, the ES complex breaks down to enzyme and
product
102
This theory states that the 3D of the active site of the enzyme is complementary to the substrate. Thus, substrate and enzyme fit together, similar to a lock and key.
fisher's template theory
103
the fisher's template theory cannot explain
the flexibility shown by enzymes
104
this theory states that conformational changes are occurring at the active site of enzymes concomitant with the combination of enzyme with the substrate
koshland's induced fit theory
105
this is the region of an enzyme where substrate molecules bind and undergo a chemical reaction
active site
106
the active site consists of amino acids residues that form ___ with the substrate (binding site) and residues (catalytic site) that catalyze a reaction of that substrate
temporary bonds
107
catalytic triad of amino acids in the catalytic site
his (57), asp (102), ser (195)
108
important amino acid at the catalytic site of chymotrypsin
his (57), asp (102), ser (195)
109
important amino acid at the catalytic site of trypsin
ser, his
110
important amino acid at the catalytic site of thrombin
ser, his
111
important amino acid at the catalytic site of phosphoglucomutase
ser
112
important amino acid at the catalytic site of alkaline phosphatase
ser
113
important amino acid at the catalytic site of acetyl cholinesterase
ser
114
important amino acid at the catalytic site of carbonic anhydrase
cysteine
115
important amino acid at the catalytic site of hexokinase
his
116
important amino acid at the catalytic site of carboxy peptidase
his, arginine, tyr
117
from the standpoint of energy, the enzymatic reactions are divided into 3 types:
exothermic/exergonic, isothermic, endothermic/endergonic
117
important amino acid at the catalytic site of aldolase
lysine
118
here energy is released from the reaction, and therefore reaction essentially goes to completion
evergonic/exothermic
119
examples of exergonic
urease enzyme
120
at equilibrium of exergonic reactions the substrate will be at ___ and the product will be at ___
0.5%; 99.5%
121
reactions for this type are generally invisible
exergonic
122
type of reaction where energy exchange is negligible and the reaction is easily reversible
isothermic
123
type of reaction where energy is consumed and external energy is to be supplied for these reactions
endergonic
124
in the body, this is usually accomplished by coupling the endergonic reaction with an exergonic reaction
endergonic
125
factors influencing enzyme activity
enzyme concentration, effect of substrate concentration, effect of concentration of products, effect of temperature, effect of hydrogen ion concentration (pH), presence of activators, presence of inhibitors, feedback inhibition and repression, stabilization and compartmentalization
126
rate of a reaction or velocity is directly proportional to the enzyme concentration , when sufficient substrate is present
enzyme concentration
127
as substrate concentration is increased, the velocity is also correspondingly increased in the initial phases, but the curve flattens afterwards
effect of substrate concentration
128
this represents the maximum reaction rate attainable in presence of excess substrate
Vmax
129
this is the concentration of substrate which permits the enzyme to achieve half Vmax
Km (Michaelis constant)
130
this is also the signature of the enzyme
Km
131
this value is a constant for an enzyme
Km value
132
It is the characteristic feature of a particular enzyme for a specific substrate
Km value
133
Type of factor where in a reversible reaction, S ↔ P, when equilibrium is reached, as per the law of mass action, the
reaction rate is slowed down. So, when product concentration is increased, the reaction is
slowed, stopped or even reversed.
Effect of Concentration of Products
134
In effect of concentration of products, in inborn errors of metabolism, one enzyme of a metabolic pathway is
blocked
135
Type of factor where the velocity of enzyme reaction increases when
temperature of the medium is increased; reaches
a maximum and then falls (Bell shaped curve).
Effect of Temperature
136
The temperature at which maximum amount of
the substrate is converted to the product per unit
time is called the
optimum temperature
137
Most human enzymes have the optimum
temperature around
37°C
138
Factor where each enzyme has an optimum pH, on both sides of which the velocity will be drastically reduced.
Effect of Hydrogen ion concentration (pH)
139
Optimum pH may vary depending on the
temperature, concentration of substrate, presence
of ions etc. Usually, enzymes have the optimum
pH _______. Some important exceptions
are ______
between 6 and 8, pepsin (with optimum pH 1-2); alkaline
phosphatase (optimum pH 9-10) and acid
phosphatase (4-5)
140
Factor where in presence of certain inorganic ions, some enzymes show higher activity. Thus, chloride ions
activate salivary amylase and calcium activate lipases.
Presence of Activators
141
Another type of activation is the ______ of an inactive pro-enzyme or zymogen to the active
enzyme.
conversion
142
BY splitting a single peptide bond, and removal of a small polypeptide from trypsinogen, the _______ is formed
active trypsin
143
types of inhibition
competitive, non-competitive, uncompetitive inhibition, allosteric regulation
144
Here inhibitor molecules are competing with the normal substrate molecules for binding to the active site of the enzyme
competitive inhibition
145
In competitive inhibition, the inhibitor is a ______ of the substrate
structural analog
146
type of inhibition which is usually reversible
competitive inhibition
147
In competitive inhibition, the excess substrate _____ the inhibition
abolishes
148
In competitive inhibition, _____ is increased in presence of competitive inhibitor but Vmax is not changed
Km
149
E + S -><- E-S -------> E + P
Competitive inhibition
150
Example of medication that exhibits competitive inhibition
metotrexate
151
type of inhibition that is usually irreversible
non-competitive inhibition
152
poisons such as ____, ____, & _____ act as irreversible non-competitive inhibitors
lead, cyanide, mercury
153
In non-competitive inhibition, substrates can bind but the reaction is
blocked
154
The Vmax is reduced but the ___ is not
Km value
155
type of inhibition that does not have any affinity for free enzyme
uncompetitive inhibition
156
this may be reversible or irreversible
157
in uncompetitive inhibition, inhibitors bind to the ____ but not the free enzyme
enzyme-substrate complex
158
in uncompetitive inhibition, both Vmax and Km are
decreased
159
Example of uncompetitive inhibition
finasteride in benign prostatic hyperplasia
160
______ has one catalytic site where the substrate binds and another separate allosteric site where the modifier binds
allosteric enzyme
161
in allosteric regulation, the binding of the regulatory molecule enhances the activity of the enzyme, this is known as
allosteric activation
162
in allosteric activation, the regulatory molecule is known as the
positive modifier
163
in allosteric regulation, the binding of the regulatory molecule inhibits the activity of the enzyme, this is known as
allosteric inhibition
164
in allosteric inihibition, the regulatory molecule is known as the
negative modifier
165
what does the body use allosteric enzymes for?
regulating metabolic pathways
166
the regulatory enzyme in a particular pathway is called the
key enzyme/rate limiting enzyme
167
The allosteric inhibitor is most effective when substrate concentration is
low
168
in allosteric regulation, when more substrate molecules are available, there is less necessity for
stringent regulation
169
in heme biosynthesis what is the end product?
heme
170
heme will allosterically inhibit the
ALA synthase
171
this is the key enzyme in heme synthesis
ALA synthase
172
another factor influencing enzyme activity, where for its mechanism, the accumulated end products binds with the enzyme and inhibits the enzyme activity
feedback inhibition
173
another factor influencing enzyme activity, where for its mechanism, the accumulated end products works as a repressor and inhibits the enzyme synthesis at a genetic level
feedback repression
174
in feedback inhibition, end products binds with the ____
active site of the enzyme
175
in feedback repression, end products binds with the _____ that encode the enzyme and prevent its synthesis
DNA of the gene
176
in this factor influencing enzyme activity, the enzyme molecules undergo usual wear and tear and finally get degraded. such degradation if prevented can lead to increased overall enzyme activity
stabilization of enzyme
177
degradation of tryptophan pyrrolase is retarded by
tryptophan
178
what stabilizes phospho fructo kinase
growth hormone
179
SH groups
papain, urease, succinate dehydrogenase
180
what stabilizes enzymes with SH groups?
glutathione
181
this is used to inhibit the enzyme thymidylate synthase
5-fluorouracil (5-FU)
181
this factor influencing enzyme activity is exhibited by certain enzyme pathways being located in mitochondria whereas others of the same pathway cytoplasmic
compartmentalization
182
this enzyme converts deoxyuridine monophosphate (dUMP) to deoxy-thymidine monophosphate (dTMP) which provides the thymine for DNA synthesis
thymidylate synthetase
183
this drug irreversibly inhibits the enzyme cyclooxygenase and interferes with the generation of prostaglandins and thromboxanes
aspirin
184
this is the secondary mediator of pain signaling
thromboxane
185
this drug is a suicide inhibitor of xanthine oxidase and is used in the treatment of gout
allopurinol
186
xanthine oxidase will recognize allopurinol as a substrate and oxidize it to create _____, which binds so tightly to the active site that it is not released and then inhibits further reactions by the enzyme
oxypurinol
187
this is a drug that is used to treat alcoholism irreversibly inhibits the enzyme aldehyde dehydrogenase leading to an accumulation of acetaldehyde whenever alcohol is ingested
disulfiram
188
acetaldehyde leads to ____ and may deter the patient from drinking alcohol
hangover symptoms
