ENZYME PART 2

Question 1

Catalytic mechanisms

Answer 1

Acid-base catalysis
Nucleophilic catalysis
Elctrophilic catalysis
Catalysis by proximity and orientation
Preferential transition state binding

Question 2

Acid-base catalysis

Answer 2

Proton donation and acceptor
Histidine

Question 3

Nucleophilic catalysis

Answer 3

Nucleophile (enzyme)
Electrophile (substrate)

Promote substitution reaction

Question 4

Serine Proteases: Catalytic Triad

Answer 4

Ser His Asp

Question 5

Ser

Answer 5

Nucleophile; Nucleophilic catalyst
Form covalent bond

Question 6

His

Answer 6

Acid base catalyst

Question 7

Asp

Answer 7

Stabilizes histidine

Question 8

Electrophilic catalysis

Answer 8

Nucleophile: Substrate
Electrophile: Enzyme
Elimination

Question 9

Electrostatic Catalysis

Answer 9

Binding substrate excludes H2O from the active site
Local dielectric constant active site resembles that in an organic solvent
Ionic interactions

Question 10

Catalysis by proximity and orientation

Answer 10

Enzyme attract substrate in certain orientation to react with cosubstrate

Question 11

Preferential transition state binding

Answer 11

Transition state has higher binding affinity than the substrate

Question 12

Regulation of activity

Answer 12

Coordination of numerous metabolic processes in the cell
Respond to changes in its environment
Grow and differentiate all in an orderly manner

Question 13

Enzyme types based on regulation

Answer 13

Constitutive
Inducible

Question 14

Constitutive

Answer 14

Produced all the time
Healthy state or normal state

Question 15

Inducible

Answer 15

Produced only when needed or in the presence of substrate

Question 16

Regulatory mechanisms

Answer 16

Feed forward
Positive feedback
Negatuve feedback
Up regulation
Down regulation
Allosteric regulation

Question 17

Allosteric site

Answer 17

Any part of the enzyme but not active site
Alters the acitivity of the enzyme

Question 18

Monod, Wyman, Chageux (MWC) Model

Answer 18

Symmetrical model
One step activation or deactivation

Question 19

Koshland, Nemethy, Filmer (KNF) Model

Answer 19

One subunit is active and the other one is not
Two step activation

Question 20

Regulation by covalent modification

Answer 20

Protein kinase - activate the enzyme
Protein phosphatase - deactivate the enzyme

Question 21

Regulation by modular proteins

Answer 21

Convert inactive enzyme into active enzyme
Promotes the phosphorylation of other protein or other enzymes

Question 22

Factors affecting enzymatic activity

Answer 22

Temp.
pH
Substrate conc

Question 23

Michelis-Menten Model

Answer 23

Applies only to enzymes that dont have multiple binding sites and whose Km is higher than the total enzyme concentration

Question 24

Km

Answer 24

Substrate conc at Vmax/2
[E][S]/[ES]

Question 25

Linewaever-Burk Plot

Answer 25

1/Vo=(Km/Vmax)1/[S] + 1/Vmax

Question 26

Enzymes are highly efficient

Answer 26

10^3 - 10^8 times faster than uncatalyzed reactions

Question 27

Product turnover per enzyme molecule

Answer 27

100-1000/sec

Question 28

Kcat=Vmax/[E]T

Answer 28

Number of processes that each active site catalyzes per unit of time

Question 29

Kcat/Km

Answer 29

Measure of the catalytic efficiency of the enzyme

Question 30

Measuring reaction velocity

Answer 30

V=delta[P]/delta[Time] or delta[S]

Question 31

Competitive inhibitors

Answer 31

Binds in free enzymes to form EI same Vmax High Km High slope

Question 32

Uncompetitive Inhibitors

Answer 32

Binds ES complex to form ESI Low Vmax Low Km Same slope

Question 33

Mixed Inhibitors

Answer 33

Binds free enzyme and ES complex Low Vmax High Km High slope

Question 34

Mixed Noncompetitive

Answer 34

Binds free enzyme allosteric to form EI Low Vmax Same Km High slope

Question 35

Enzymes as drugs

Answer 35

Oncolytic agents Anticoagulant Enzyme replacement therapy

Question 36

Oncolytic agents

Answer 36

L-asparagine Neuraminidase

Question 37

Anticoagulant

Answer 37

Tissue plasmin activator Streptokinase

Question 38

Enzyme replacement therapy (ERT)

Answer 38

Collagenase Papain Trypsin and chymotripsin

Question 39

Enzymes used in clinical diagnosis

Answer 39

Present in highest conc Present at low level Used as reagent

Question 40

Enzymes present in highest concentration

Answer 40

Has systemic functional role Thrombin in blood coagulation

Question 41

Enzymes present at low level

Answer 41

No systemic functional role Indicators of disease of organs and tissues

Question 42

Enzymes used as reagent

Answer 42

Creatinase, cholesterol oxidase, glucose peroxidase