GENERAL MICROBIOLOGY - T.P. Pyrog - 2004

20. METABOLIC REGULATION

20.2. REGULATION OF ENZYME ACTIVITY

Regulation at the level of enzyme activity is typically characteristic only of Key Enzymes in cellular METABOLISM. The catalytic activity of enzymes involved in a specific biosynthetic pathway can vary: it may increase under the action of a positive effector or decrease under the action of a negative effector. In the case of end-product inhibition (feedback inhibition), the final product suppresses The activity of the first enzyme participating in the given reaction chain. This type of regulation is also known as feedback inhibition (Fig. 20.4).

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Fig. 20.4. Feedback Introduction/15.html">Regulation of enzyme Activity (schematic diagram)

When pyrimidine NUCLEOTIDES accumulate within The Cell, CTP inhibits the activity of aspartate transcarbamylase—the enzyme that catalyzes the first step of their synthesis (Fig. 20.6).

Fig. 20.5. Scheme of regulation of aspartate transcarbamylase activity

It should be noted that through The regulation of enzyme synthesis (Induction and Repression), Cells can adapt to changing growth conditions only slowly. These mechanisms can be considered as forms of coarse regulation. A more rapid cellular adaptation to changing environmental conditions is achieved through the regulation of enzyme activity. Alteration in the activity of a key enzyme manifests immediately—this represents fine-tuning regulation.