Question

Phosphotransacetylase, catalyzes this reaction:

CoASH + acetyl phosphate -> acetyl CoA + Pi

The mechanism is thought to involve an oxyanion hole and a covalent ester intermediate is proposed.

Arg 76 (R76) is proposed to play a role in allosteric inhibition of phosphotransacetylase by ATP.

Design an experiment to test the hypothesis that Arg 76 (R76) plays a role in allosteric inhibition. Predict the results you would get if the hypothesis is correct.

Answer 1

Mentioned enzymatic reaction cannot be possible if ATP is present as ATP act as allosteric inhibitor of enzyme phosphotransacetylase.

ATP binds to arginine R76 of amino acid sequence of enzyme. If we use site specific mutagenesis process that leads to change of arginine to alanine at position 76 then ATP won't be able to bind as atp is negative which binds with positive charge arginine and if arginine is replaced with alanine which is small neutral amino acid then ATP cannot bind to enzyme.

So this mutated enzyme function even in present of ATP.

Hope it's clear..thanks