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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
Q

Cofactor, vitamin, chemical group transferred

menaquinone

A

from vitamin K

transfers carbonyl group and electrons

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26
Q

Cofactor, vitamin, chemical group transferred

flavin mononucleotide

A

riboflavin B2

transfers electrons

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27
Q

Cofactor, vitamin, chemical group transferred

NAD and NADP

A

from niacin (B3)

transfers electrons

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28
Q

lipoamide

A

from lipoic acid

transfers electrons, acyl groups

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29
Q

biotin

A

from biotin vit

transfers CO2

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30
Q

tetrahydrofolic acid

A

from vitamin B9 (folic acid)

transfers methyl groups and formyl groups

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31
Q

coenzyme F420

A

riboflavin B2

transfers electrons

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32
Q

B1

A

produces thiamine pyrophosphate

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33
Q

B2

A

also called riboflavin

produces coenzyme F420

34
Q

B3

A

also called niacin

produces NAD NADP

35
Q

B5

A

also called panthothenic acid

produces Coenzyme A

36
Q

B6

A

also called pyridoxine

produces pyridoxal phosphate

37
Q

B9

A

folic acid

produces tetrahydrofolic acid

38
Q

B12

A

produces methylcobalamin

39
Q

Ascorbic acid

A

comes from VC, transfers electrons

VC produces lysyl hydroxylase

40
Q

Scurvy

A

vitamin C deficiency (lysyl hydroxylase)

decreased collagen assembly

41
Q

Ariboflavinosis

A

riboflavin B2 required for FAD synthesis
reduced GLUTATHIONE REDUCTASE activity, requires FAD
lesions in corner of mouth and on lips, UV sensitivity

42
Q

dehydrogenases bind

A

NAD+’s

43
Q

cofactors vs coenzymes

A

cofactors are metal ions that associate with protein enzymes via noncovalent interactions

coenzymes

small organic molecules mostly derived from vitamins

44
Q

cosubstrate

A

coenzymes that associate with enzyme temporarily. they bind in one state and detach in another. example: NAD

45
Q

prosthetic group

A

coenzymes associate permanently with enzymes

include flavin adenin dinucloetide (FAD), flavin mononucecleotide (FMN) and heme

46
Q

reductase

A

transfers electrons or hydrogen

47
Q

oxidase

A

accepts electrons or hydrogen

48
Q

alcohol dehydrogenase

A

ADH

converts alcohols to aldehydes or ketones with the reduction of NAD (cofactor) to NADH

49
Q

what is critically needed for transferase reactions

example

A

a third molecule to donate a group to transfer (ATP for P for example)

kinase receptors is the example

50
Q

kinase receptors

A

transferases

phosphorylate themselves and others

usually transfer Ps from ATP to serine, threonine and tyrosine on another protein or themselves

51
Q

how do hydrolases works?

A

they transfer functional groups to water and thereby break covalent bonds

52
Q

Disaccharidases

A

hydrolases

disaccharidases cleave double sugars to single sugars

defect in LACTASE leads to lactose intolerance

53
Q

Lyases

A

enzyme that catalyzes addition or removal of groups to form double bonds

54
Q

Lyases: example of rxn and enzyme

A

Fructose 1,6, bisphosphate —>
Dihydroxyacetone (DHAP) + Glyceraldehyde-3-GAP (GAP)

second step of glycolysis ^

rxn is catalyzed by an ALDOLASE

55
Q

isomerase

A

enzyme that catalyzes isomerization i.e. intramolecular group transfer, product is just an isomer of the substrate

56
Q

transition state

A

intermediate structure that is not the substrate and not yet the product

unstable and highest free energy

57
Q

michaelis-mentin formula

A

velocity of enzyme = ((Vmax)(Substrate))/((Km+(substrate))

58
Q

x intercept of lineweaver-burke graph

A

-1 / Km

59
Q

y intercept of lineweaver burk graph

A

1 / Vmax

60
Q

slope of lineweaver burk graph

A

Km/Vmax

61
Q

V0 = Vmax (s) / [(s) + (km)]: this equation tells us that

A

when s = km, then V0 = vmax/2

62
Q

when vmax/2, then V0 =

A

Vmax/2 = V0

V0 = Vmax (s)/((s)(km))

63
Q

how to calculate Km and Vmax

A

reciprocal of michaelis menton

1/V0 = (km)/(Vmax)((s)) + 1/ Vmax

64
Q

-1/km =

A

x intercept on lineweaver burke plot

65
Q

1/vmax =

A

y intercept on the lineweaver burke plot

66
Q

Competitive – Noncompetitive – Uncompetitive Inhibitors

A

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
Q

Reversible Inhibitors

use what kind of bonds

A

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
Q

Irreversible inhibition

A

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
Q

how does pH alter enzyme activity?

A

hydrogen disrupts ionic bonds that contribute to enzyme’s shape

70
Q

Allosteric enzymes

A

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
Q

An allosteric inhibitor pushes the sigmoid to the

A

right

72
Q

An allosteric activator pushes the sigmoid to the

A

left

73
Q

Acetyl CoA

A

pyruvate –> oxaloacetate
positive allosteric stimulus is acetyl-CoA

positive allosteric stimulator that stimulates gluconeogensis

rxn
pyruvate –> oxaloacetate

Acts on
pyruvate carboxylase

74
Q

Fructose 2,6 BP

A

positive effector that stimulates glycolysis

acts on
phosphofructokinase-1

rxn
fructose

75
Q

Citrate

A

allosteric inhibitor of the Fructose–6P –> fructose 1,6-BP

76
Q

Glucose 6-P

A

Glucose—> glucose 6–P

negative allosteric effect on hexokinase

77
Q

ATP

A

positive stimulus on Aspartate carbomylase

rxn

Carbomyl-P + aspartate –> carbamoyl aspartate

in pyrimidine synthesis

78
Q

CTP

A

allosteric inhibitor of Aspartate carbomylase

rxn

Carbomyl-P + aspartate –> carbamoyl aspartate

in pyrimidine synthesis

79
Q

isozymes

A

enzymes that resemble one another, have the same substrate to react with. isoforms appear in different tissues

80
Q

MI enzymes that can be measure

A

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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