Question

A competitive inhibitor of succinic dehydrogenase is
A) 𝝰-ketoglutarate
B) Malate
C) Malonate
D) Oxaloacetate

Answer 1

It is possible to activate or suppress enzymes in various ways. With a dramatic shift in pH, temperature or ionic concentration, precise inhibition is possible. By using unique enzyme inhibitors, much more information can be obtained. Succinate dehydrogenase (SDH) is the only inner mitochondrial membrane-bound enzyme in the citric acid cycle, and the rest of the enzymes are located in a soluble form in the matrix. Such enzyme kinetic analysis can shed light on the mechanism of enzyme activity.

Complete answer:
Competitive Inhibitors:

This is the most easy and obvious type of inhibition of enzymes - and the name tells you exactly what happens.
The inhibitor has a similar form to the enzyme's normal substrate and competes for the active site with it. However nothing happens to it once it is connected to the active site. It doesn't respond - it just gets in the way, basically.
Malonate ions inhibiting the succinate dehydrogenase enzyme are a clear example of this. The transformation of succinate ions into fumarate ions is catalysed by this enzyme. The contemporary titles are:
i) Propanedioate: malonate
ii) Butanedioate: succinate
iii) Trans-Butenedioate: Fumarate

Malonate is a competitive inhibitor of the malonate succinate dehydrogenase enzyme that binds without reacting to the enzyme's active site and thus competes with the enzyme's normal succinate substrate.To deduce the structure of the active site in that enzyme, malonate was used as a competitive inhibitor of succinate dehydrogenase. The chemical malonate reduces cellular respiration.

Thus the correct answer is option (C) Malonate.

Note: If the succinate ions have a higher concentration than the malonate ions, they would have more access to the site than the malonate ions by chance. That means that by increasing the substrate concentration, you can overcome the effect of a competitive inhibitor.