Question

19. Acetylcholinesterase is an enzyme with a very high frequency of appearance in BMB 401 worksheets. (Recall question #10, above.) This enzyme hydrolyzes acetylcholine. The activity of acetylcholinesterase is important for modulating synaptic transmission. Some bioweapons (nerve HO active site of the acetylcholinesterase (anionic site +esteric site), and based on what you know about serine reactivity, how do you think the nerve agent works? Serine Estenic Se Acetylcholinesterase How many functional groups in the peptide MDFGRKCDE can gain or lose a proton? 20. 21. Some key points in the titration curve of an amino acid are labeled A to G (at right). Would this amino acid serve as a good buffer at any of the labeled points? If not, explain why not, and if so, indicate at which points it would serve as a good buffer. 12

Answer 1

Ans 19) Acetylcholisterase is an enzyme which helps in hydrolyzing the acetylcholine that is a neurotransmitter. When a nerve agent is added, it interferes with the binding of the enzyme and hence prevents the acetylcholisterase from binding to the acetylcholine. As the nerve agent binds to the anion site of the acetylcholisterase and does prevent it from binding to acetylcholine which causes the inhibition. The activity of the acetylcholine cannot be stopped. As soon as the acetylcholine is released at the axon terminal and helps in post synaptic transmission that can be stopped by acetylcholisterase but as the nerve agent binds to the enzyme, the synaptic transmission cannot be inhibited any more. The nerve agent forms a covalent bond with the active site of the enzyme and hence this binding prevents the acetylcholine from being broken down. This tends to increase the concentration of acetylcholine and leads to continuous nerve impulse transmission and contraction of muscle.