Enzyme Kinetics

Question 1

What is Kd?

Answer 1

[S] where half is bound. Low conc = high affinity

Question 2

Enzymes bind and stabilize the ________.

Answer 2

Transition state. (induced fit)

Question 3

Difference between cofactor & coenzyme?

Answer 3

CoFactor: usually metal, doesn’t donate (Fuck off; I’m not giving you anything)
Coenzyme: donates chemical group

Question 4

What is Km?

Answer 4

[S] needed for enzyme to go at 1/2 Vmax. The lower the Km, the less it needs to operate efficiently.

Question 5

What is Kcat?

Answer 5

“turnover number” for an enzyme. It measures the number of substrate molecules turned over (into product) per enzyme molecule, per second. (inverse = how long it takes to convert each substrate molecule). Higher = faster

Question 6

Kcat / Km

Answer 6

Measure of efficiency.
THe lower km is, the less substrate it needs to operate more effficiently. The higher kcat is, the faster its going and the more efficient it is. kcat/km is overall efficiency of the enzyme. When youre close to 10^8 or 10^9, you’re approaching catalytic perfection. The only thing limiting enzyme by that point is diffusion rate (how quickly it finds the substrate)

Question 7

Describe the 4 inhibitors

Answer 7

Competitive: competes for active site
Uncompetitive: binds outside active site, but only ES
Mixed: binds outside active site, but can bind either E or ES (non comp is a type)
Irreversible: self explanatory

Question 8

Describe the graph changes for inhibitors

Answer 8

Comp = slope
Uncomp = X/Y-int
Mixed = both

Question 9

What are the 4 types of enzyme regulation mechanisms?

Answer 9

Allosteric: binding of another molecule changes conformation
Covalent: phosphorylation
Binding regulatory: like allosteric, but with peptide
Proteolytic cleavage (inactive –> active)