Question

(1). Most vitamins are coenzymes or precursors to coenzymes. Please do literature research and give an example to explain how the vitamin affects the activity of the enzyme.

(2). Enzymes can be good targets for therapeutic drug design. Some drugs are enzyme inhibitors. Please give an example to explain how the drug functions through the inhibition of the enzyme.

(3). Amylase is a digestive enzyme that breaks down starch and is secreted in the mouth of humans. Amylase functions well in the mouth but ceases to function once it hits the acidic stomach environment. Explain why amylase does not function in the stomach.

Answer 1

1.
PLP is an active form of Vitamin B6.
It acts as a coenzyme to several enzymes.
It covalently binds to substrate and acts as an electrophilic catalyst.
It stabilizes different carbanion reaction intermediates.
Ex: Aminotransferases.

2.
Drug = Alpha amanitin
Inhibited enzyme = RNA polymerase II

Alpha-amanitin is an octapeptide isolated from Amanita phalloides.
It interacts with the bridge helix in RNA pol II which inhibits the translocation of RNA and DNA thereby preventing the addition of new nucleotides.

3.
pH in the stomach = 1 to 2.
Amylase is denatured at acidic pH.
It can function only in the mouth where the pH is suitable for its activity.