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MCM > Enzymes and Isoenzymes > Flashcards

Enzymes and Isoenzymes Flashcards

1
Q

Sir Archibald Edward Garrod

A

First to make a connection between disease and fundamental errors of biochemical reactions

coined term “inborn errors of metabolism”

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2
Q

Mass action

A

La Chatelier’s principle

you can alter one side by adding or removing agents from the products or reactants side to push the RXN in the opposite direction

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3
Q

Physiological acids

A

beta-hydroxybuteric acid
acetone
acetoacetic acid

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4
Q

Physiological bases

A

bicarbonate

NH3

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5
Q

There are two things enzymes DO and at least one thing

A

They lower the energy of activation required to transform a substrate into an activated intermediate form, and they speed up the velocity of the rxn by doing so

they do not alter gibbs free energy or substrate concentrations

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6
Q

Oxidoreductases

A

enzyme that transfers electrons from a donor (reducing agent) to a acceptor (oxidizing agent)

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7
Q

Transferases

A

transfer a functional group between molecules

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8
Q

Isomerases

A

rearrange/isomerize molecules

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9
Q

Lyases

A

add or remove atoms to a double bond or form a double bond

“synthases”

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10
Q

Ligases

A

“synthetases”

form bonds with hydrolysis of ATP

C-O
C-S
C-N
C-C

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11
Q

Hydrolases

A

cleave bonds via addition of water

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12
Q

Active Site

A

contains a unique microenvironment usually void of water and controls the proper shape, pH, and polarity for substrte binding and chemical reactivity

shape, pH, polarity controlled
void of water

defines microenvironment

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13
Q

Chymotrypsin

A

serine protease

USES serine to cleave proteins, not cleaving proteins AT serine

catalytic triad
three chains
two intra and two inter-strand disulfide linkages

catalytic triad converts serine 195 into a potent nucleophile

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14
Q

Mechanism of peptide hydrolysis

A

you have interacting amino acids that can stabilize, alter, and the rejuvenate one another while interacting with the peptide bonds on a protein

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15
Q

cofactors

A

small molecules that contribute to the chmeical reaction of the enzyme

many different roles in catalysis

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16
Q

enzymes that use the same cofactors

A

share the same mechanism of catalysis

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17
Q

nomenclature of cofactors ‘

apoenzyme vs haloenzyme

A

apoenzyme

enzyme without its cofactor

haloenzyme

cofactor bound and catalytically active

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18
Q

metal cofactors are

A

positively charged
stable coordination of active site groups
contribute to chemical reactivity

example:

ZINC activates H2O to form OH- nucleophile

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19
Q

metal cofactors (metals)

A

Cu, Fe, Mg, Se, Zn

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20
Q

Coenzymes

A

small organic molecules often derived from vitamins

bound tightly, called prosthetic group

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21
Q

Cofactor, vitamin, chemical group transferred

Thiamine pyrophosphate

A

from Vitamin B1

transfers 2 carbon groups

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22
Q

Cofactor, vitamin, chemical group transferred

pyridoxal phosphate

A

pyridoxine (vit B6)

transfers amino and carbonyl groups

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23
Q

Cofactor, vitamin, chemical group transferred

methylcobalamin

A

comes from B12

transfers acyl groups

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24
Q

Cofactor, vitamin, chemical group transferred

coenzyme A

A

panthothenic acid

vit B5

chemical groups transferred: acetyl groups

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25
Cofactor, vitamin, chemical group transferred menaquinone
from vitamin K | transfers carbonyl group and electrons
26
Cofactor, vitamin, chemical group transferred flavin mononucleotide
riboflavin B2 transfers electrons
27
Cofactor, vitamin, chemical group transferred NAD and NADP
from niacin (B3) transfers electrons
28
lipoamide
from lipoic acid transfers electrons, acyl groups
29
biotin
from biotin vit transfers CO2
30
tetrahydrofolic acid
from vitamin B9 (folic acid) transfers methyl groups and formyl groups
31
coenzyme F420
riboflavin B2 transfers electrons
32
B1
produces thiamine pyrophosphate
33
B2
also called riboflavin produces coenzyme F420
34
B3
also called niacin produces NAD NADP
35
B5
also called panthothenic acid produces Coenzyme A
36
B6
also called pyridoxine produces pyridoxal phosphate
37
B9
folic acid produces tetrahydrofolic acid
38
B12
produces methylcobalamin
39
Ascorbic acid
comes from VC, transfers electrons VC produces lysyl hydroxylase
40
Scurvy
vitamin C deficiency (lysyl hydroxylase) decreased collagen assembly
41
Ariboflavinosis
riboflavin B2 required for FAD synthesis reduced GLUTATHIONE REDUCTASE activity, requires FAD lesions in corner of mouth and on lips, UV sensitivity
42
dehydrogenases bind
NAD+'s
43
cofactors vs coenzymes
cofactors are metal ions that associate with protein enzymes via noncovalent interactions coenzymes small organic molecules mostly derived from vitamins
44
cosubstrate
coenzymes that associate with enzyme temporarily. they bind in one state and detach in another. example: NAD
45
prosthetic group
coenzymes associate permanently with enzymes include flavin adenin dinucloetide (FAD), flavin mononucecleotide (FMN) and heme
46
reductase
transfers electrons or hydrogen
47
oxidase
accepts electrons or hydrogen
48
alcohol dehydrogenase
ADH converts alcohols to aldehydes or ketones with the reduction of NAD (cofactor) to NADH
49
what is critically needed for transferase reactions example
a third molecule to donate a group to transfer (ATP for P for example) kinase receptors is the example
50
kinase receptors
transferases phosphorylate themselves and others usually transfer Ps from ATP to serine, threonine and tyrosine on another protein or themselves
51
how do hydrolases works?
they transfer functional groups to water and thereby break covalent bonds
52
Disaccharidases
hydrolases disaccharidases cleave double sugars to single sugars defect in LACTASE leads to lactose intolerance
53
Lyases
enzyme that catalyzes addition or removal of groups to form double bonds
54
Lyases: example of rxn and enzyme
Fructose 1,6, bisphosphate ---> Dihydroxyacetone (DHAP) + Glyceraldehyde-3-GAP (GAP) second step of glycolysis ^ rxn is catalyzed by an ALDOLASE
55
isomerase
enzyme that catalyzes isomerization i.e. intramolecular group transfer, product is just an isomer of the substrate
56
transition state
intermediate structure that is not the substrate and not yet the product unstable and highest free energy
57
michaelis-mentin formula
velocity of enzyme = ((Vmax)(Substrate))/((Km+(substrate))
58
x intercept of lineweaver-burke graph
-1 / Km
59
y intercept of lineweaver burk graph
1 / Vmax
60
slope of lineweaver burk graph
Km/Vmax
61
V0 = Vmax (s) / [(s) + (km)]: this equation tells us that
when s = km, then V0 = vmax/2
62
when vmax/2, then V0 =
Vmax/2 = V0 V0 = Vmax (s)/((s)(km))
63
how to calculate Km and Vmax
reciprocal of michaelis menton 1/V0 = (km)/(Vmax)((s)) + 1/ Vmax
64
-1/km =
x intercept on lineweaver burke plot
65
1/vmax =
y intercept on the lineweaver burke plot
66
Competitive -- Noncompetitive -- Uncompetitive Inhibitors
Competitive inhibitors bind and compete with the substrate for the active site of an enzyme. CI's increase the Km Uncompetitive inhibitors bind to the enzyme-substrate complex at an allosteric site (meaning they dont prevent ES formation). UI's alter bother Km and Vm Noncompetitive inhibitors bind either the enzyme or the enzyme-substrate complex. Affects only the Vmax.
67
Reversible Inhibitors use what kind of bonds
hydrogen bonds, hydrophobic bonds, ionic bonds, all non-covalent bonds : bind to the enzyme but do not undergo any chemical reactions with the enzyme once bound
68
Irreversible inhibition
covalently modifies enzyme, inhibition therefore cannot be reversed. they work by modifying the active site of the enzyme, but do not destroy the overall protein structure
69
how does pH alter enzyme activity?
hydrogen disrupts ionic bonds that contribute to enzyme's shape
70
Allosteric enzymes
an enzyme whose whose activity is modulated through noncovalent binding of a specific metabolite (called an allosteric effector molecule) they do not follow michaelis menten kinetics produce a sigmoid curve rather than a hyperbolic curve
71
An allosteric inhibitor pushes the sigmoid to the
right
72
An allosteric activator pushes the sigmoid to the
left
73
Acetyl CoA
pyruvate --> oxaloacetate positive allosteric stimulus is acetyl-CoA positive allosteric stimulator that stimulates gluconeogensis rxn pyruvate --> oxaloacetate Acts on pyruvate carboxylase
74
Fructose 2,6 BP
positive effector that stimulates glycolysis acts on phosphofructokinase-1 rxn fructose
75
Citrate
allosteric inhibitor of the Fructose--6P --> fructose 1,6-BP
76
Glucose 6-P
Glucose---> glucose 6--P negative allosteric effect on hexokinase
77
ATP
positive stimulus on Aspartate carbomylase rxn Carbomyl-P + aspartate --> carbamoyl aspartate in pyrimidine synthesis
78
CTP
allosteric inhibitor of Aspartate carbomylase rxn Carbomyl-P + aspartate --> carbamoyl aspartate in pyrimidine synthesis
79
isozymes
enzymes that resemble one another, have the same substrate to react with. isoforms appear in different tissues
80
MI enzymes that can be measure
LDH-1 2-3 days after MI CK-MB 12-14 hrs after MI Troponin I 12-24 hrs after MI AST/SGOT1 12-16 hrs after MI

MCM (22 decks)

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