Enzyme kinetics 3

Question 1

What is a hapten?

Answer 1

a small molecule that reacts specifically with an antibody but is incapable of stimulating antibody production except in combination with an associated protein molecule

Question 2

What is the affinity of catalytic antibodies?

Answer 2

10^5 - 10^9

Question 3

What is an abzyme?

Answer 3

a catalytic antibody that has structural complementarity with the transition state of the substrate catalysed by a reaction.

Question 4

Why don’t you want abzymes to have high affinity for the substrate?

Answer 4

Because they would stabilise the substrate and therefore not encourage a reaction.

Question 5

Cocaine acts as a what?

And so how does this increase synaptic firing?

Answer 5

serotonin-norepinephrine-dopamine reuptake inhibitor. Therefore cocaine increases neurotransmitter in the cleft. Hence synapses keep firing

Question 6

What does Butyrylcholinesterase (BChE) hydrolyses?

Answer 6

Butyrycholine (but also cocaine obvs)

Question 7

Human esterases are slow to degrade cocaine. True or False?

Answer 7

True

Question 8

How many isoforms of butyrylcholinesterase are found in the liver, brain and heart?

Answer 8

> 11, slightly different sequences but same chemistry

Question 9

What is the catalytic triad of butyrylcholinesterase?

Answer 9

glutamate, histidine and serine

Question 10

What is the function of the carrier protein?

Answer 10

To elicit an immune response

Question 11

Why is the length of the linker between the carrier protein and hapten?

Answer 11

• Too long –> linker will be cleaved by proteases

- Too short –> antibodies will only bind carrier protein

Question 12

Can radiolabelling be used to measure how good hapten carrier binding is?

Answer 12

Yes

Question 13

What is APO?

Answer 13

‘without the substrate’

Question 14

What is cocaine converted post abzyme breakdown?

Answer 14

Ecgonine methyl and benzoate

Question 15

What is a prodrug?

Answer 15

A compound that is converted in the body to a pharmacologically active drug. e.g. aspirin is activated in the body

Question 16

What are the benefits of prodrugs?

Answer 16

The principle is that it is possible to reach the site of interest without the side effects else where.

Question 17

Can catalytic antibodies be used to activate prodrugs?

Answer 17

Yes

Question 18

What are the limitations of abzymes?

Answer 18

• abzymes can bind the product tightly so there it doesn’t readily release them and so catalysis is slow or prevented
• difficult to synthesis hapten
• some haptens fail to generate antibodies against it
• catalytic efficiency depends on the solvent exposed binding site (where your CDR loops are, If active site is deep in the groove substrates wont reach and will lower kinetics)