Biochemistry - Chemical Reactions in Living Cells, Volume 3 - D. Metzler 1980
Metabolism of Nitrogen-Containing Compounds
Histidine Metabolism
Regulation of Amino Acid Metabolism
When Histidine is present in excess within bacterial Cells, the synthesis of all Enzymes involved in histidine Biosynthesis is repressed. This is because these genes are clustered together into a single Operon [144]. Detailed information on operon Functions can be found in Chapter 15, Section B, 1. It is important to bear in mind that the 'coordinated repression' of a series of enzymes organized into a single operon is a hallmark of bacterial cells. The regulation of Amino acid METABOLISM in eukaryotes apparently operates quite differently and remains insufficiently understood to date [145].
Histidine itself also takes part in the regulation of its own synthesis by acting as an allosteric inhibitor of the first enzyme in the biosynthetic pathway—specifically, the enzyme that catalyzes step a in Fig. 14-28. Thus, whenever excess histidine accumulates, its biosynthesis is immediately inhibited.
Similar phenomena of repression and feedback inhibition operate in many amino acid biosynthetic pathways. Comprehensive reviews on this topic are available [22, 146].
Last update: 06/08/2026
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