Enzyme inhibitors

Question 1

Reversible inhibitors and the three classes

Answer 1

go through cycles of association and disassociation with the enzyme
competitive
non competitive
uncompetitive

Question 2

irreversible inhibitors

Answer 2

covalently modifies functional group on enzyme
no off rate
does inactive enzyme

Question 3

competitive inhibition

Answer 3

competes with substrate for active site of enzyme
does not permanently inactive the enzyme as it dissociates

Question 4

Ki

Answer 4

inhibition constant
[E][I]/[EI]
concentration of [I] to produce half maximum inhibition

Question 5

competitive inhibition: Km and Vmax

Answer 5

Km increases in the presence of an inhibitor (more substrate needed to reach Vmax)
Vmax is unchanged

Question 6

alpha Km

Answer 6

observed Km in the presence of an inhibitor (apparent Km)

Question 7

Non competitive inhibition

Answer 7

binds to the free enzyme and the enzyme substrate complex, but at a different site to the substrate
bound inhibitor does not inactive the enzyme (can dissociate)
changes 3D shape of enzyme so that it can still bind the substrate but is not in optimal arrangement (slows rate of catalysis)
cannot go from ESI to product

Question 8

Non competitive inhibition, Vmax and Km

Answer 8

decreases concentration of functional enzyme
Vmax is dependent on Et
Vmax reduced
substrate affinity remains unchanged so Km remains same

Question 9

uncompetitive inhibition

Answer 9

binds to a site different to where the substrate binds, and it binds to the ES complex only
doesnt inactivate the enzymee

Question 10

effect of uncompetitive inhibition on Vmax and Km

Answer 10

decreases Vmax
lowers Km

Question 11

lineweaver burke plot

Answer 11

tells us what type of inhibitor it is based on effects on Km and Vmax
also allows us to calculate Ki (how much inhibitor needed for 50% inhibition)

Question 12

mechanism based irreversible inhibitors

Answer 12

hijack normal enzyme reaction mechanism
can be selective to a single protease

Question 13

types of enzyme regulation

Answer 13

allosteric modulation
reversible covalent modification
proteolytic cleavage
feedback regulation

Question 14

allosteric enzyme modulation

Answer 14

allosteric modulators/effectors bind to an enzyme away from active site and either activate or deactivate it
changes shape of active site

Question 15

reversible covalent modification

Answer 15

addition of functional group to amino acid residues on enzyme
adenylation
phosphorylation
ribosylation
methylation
activate/inactivate depending on the enzyme/tissue etc
all reversible

Question 16

proteolytic cleavage

Answer 16

enzymes produced in their inactive form as proenzymes/zymogen
these enzymes are cleaved by another protease to activate them
reshaping of active site

Question 17

feedback regulation

Answer 17

end product of an enzymatic pathway inhibits an upstream enzyme to decrease rate of production