Regulation of metabolism

The regulation of metabolism

Microorganisms, like the rest of us, live in a changing world, and their needs do not always remain the same. It would be highly inefficient and (frequently wasteful) if all their metabolic reactions were going on with equal intensity all the time, regardless of whether they were needed. Over evolutionary time, regulation systems have developed, so that metabolism is tailored to the prevailing conditions.

Essentially, this regulation involves controlling the activity of enzymes which direct the many biochemical reactions occurring in each cell. This can be done by:

·              directly affecting enzyme activity, or

·              indirectly, at the genetic level, by controlling the level at which enzymes are synthesised.

Direct control of enzymatic activity occurs by the mechanism of feedback inhibition, whereby the final product of a metabolic pathway acts as an inhibitor to the enzyme that catalyses an early step (usually the first) in the pathway. It thus prevents more of its own formation. When the concentration of the product subsequently falls below a certain level, it is no longer inhibitory, and biosynthesis resumes.