A regulatory enzyme in a metabolic pathway is modulated by both product inhibiti

Question

A regulatory enzyme in a metabolic pathway is modulated by both product inhibition, at an allosteric site, as well as a positive allosteric effect of a metabolite

a. Draw the PROBABLE plots for this enzymes velocity ( Y axis) versus [substrate] under three conditions:

i. control conditions- substrate and enzyme only

ii: substrate and enzyme in the presence of the POSITIVE allosteric modifier, a pathway metabolite

iii: substrate and enzyme in the presence of the NEGATIVE allosteric modifier, the enzyme product

c. Draw the probable 1/v versus 1/ [S] plot for the three conditions [ all shown on the SAME PLOT, for comparison] above that correspond to your rendition of the v vs. [S] plots under :

i. control conditions

ii: in the presence of the POSITIVE allosteric modifier, a pathway metabolite

iii: in the presence of the NEGATIVE allosteric modifier, the enzyme product

Explanation / Answer

Based on the given data, allosteric regulation is one of the regulation mechanisms, in which the activity of the enzyme is regulated by binding of effector molecule to the enzyme’s allosteric site. For example, Aspartate transcarbamoylase is a multi- identical subunit protein complex that catalyzes the first step in the biosynthesis of pyrimidines. This enzyme undergoes cooperative allosteric transitions.

a) (i) (ii) (iii)

For example, consider the following data,

The graph with control conditions, positive and negative allosteric modifier is a follows:

(c) (i) (ii) (iii)

Thus, the graph is as follows:

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