Enzyme kinetics

Question 1

two models for enzymatic reactions

Answer 1

1. lock and key model
   - substrate fits into enzyme like a key in a lock
2. Induced fit model
   - substrate retains shape but enzyme changes shape to fit substrate

Question 2

5 Types of Enzyme regulation

Answer 2

1. Allosteric regulation
2. feedback regulation
3. covalent modification
4. proteolytic cleavage
5. Isozyme regulation

Question 3

Allosteric regulation

Answer 3

binding of another molecule to the enzyme alters its configuration such that activity is increased or decreased (via activators and inhibitors at site other than active site)

Question 4

Feedback regulation

Answer 4

in some reactions, the reaction product can regulate its own further production

Question 5

covalent modifications

Answer 5

catalytic activity of many enzymes can be regulated by the covalent attachment of a modifying group (like phosphoryl, ADP-ribose, adenylation

Question 6

proteolytic cleavage

Answer 6

modification of a protein like chymotrypsin—>trypsin to activate/ inactivate

Question 7

isozyme regulation

Answer 7

enzyme with similar structure can both perform similar functions on substrate, differing in Km and Vmax

Question 8

Major types of enzyme regulation by covalent modifications

Answer 8

Phosphorylation - adds phosphate
Adenylation- adds AMP
ADP-Ribosylation– adds ADP ribose
Methylation- adds methyl

Question 9

7 Qualities of allosteric enzymes (just know generally)

Answer 9

feedback inhibition is impossible
do not follow MM kinetics
one or more allosteric sites
allosteric sites are distinct from substrate binding site
composed of multiple subunits
positive effectors active, negative effectors inhibit
catalyze irreversible reactions

Question 10

T & R states of allosteric enzymes

Answer 10

T State

- The binding of first substrate to the enzyme is difficult as the subunits are in the conformation with a low affinity for that substrate
- Inhibitors of allosteric enzymes bind more tightly to the T state

R State

- The binding of first substrate changes its own subunit and adjacent subunit to the high-affinity conformation (like Hb)
- Activators of allosteric enzymes bind more tightly to the high affinity R state

Question 11

What toxin causes Gsalpha-Arg-ADP-ribosylation

Answer 11

cholera

Question 12

what toxin causes EF1-dipthamide-ADP ribosylation?

Answer 12

diphtheria

Question 13

what toxin casues Gialpha-Cys-ADPribosylation

Answer 13

pertussis

Question 14

What protein ADP ribosylates GTP binding proteins Rho and Ras?

Answer 14

Botulinum C3