ⓘ Imidazoleglycerol-phosphate dehydratase. In enzymology, an imidazoleglycerol-phosphate dehydratase is an enzyme that catalyzes the chemical reaction D-erythro-1 ..


ⓘ Imidazoleglycerol-phosphate dehydratase

In enzymology, an imidazoleglycerol-phosphate dehydratase is an enzyme that catalyzes the chemical reaction

D-erythro-1-imidazol-4-ylglycerol 3-phosphate ⇌ {\displaystyle \rightleftharpoons } 3-imidazol-4-yl-2-oxopropyl phosphate + H 2 O

Hence, this enzyme has one substrate, D-erythro-1-imidazol-4-ylglycerol 3-phosphate, and two products, 3-imidazol-4-yl-2-oxopropyl phosphate and H 2 O. This reaction is the sixth step in the biosynthesis of histidine in bacteria, fungi and plants.

This enzyme belongs to the family of lyases, specifically the hydro-lyases, which cleave carbon-oxygen bonds. The systematic name of this enzyme class is D-erythro-1-imidazol-4-ylglycerol-3-phosphate hydro-lyase. Other names in common use include IGP dehydratase, and D-erythro-1-imidazol-4-ylglycerol 3-phosphate hydro-lyase. This enzyme participates in histidine metabolism as it is involved in the 6th step of histidine biosynthesis as part of a nine step cyclical pathway.

There are two isoforms of IGPD; IGPD1 and IGPD2. The different isoforms are highly conserved with only 8 amino acids differing between them. These subtle differences however affect their activity but as yet it is unknown how.

In most organisms IGPD is a monofunctional protein of about 22 to 29 kD. In some bacteria such as Escherichia coli, it is the C-terminal domain of a bifunctional protein that include a histidinol-phosphatase domain. In E. coli, this is the protein encoded by the hisB gene.


1. Inhibition

Certain compounds that inhibit IGPD have been used as herbicides as animals do not have this protein. One of these inhibitors is 3-Amino-1.2.4-triazole 3-AT, which has also been used as a competitive inhibitor of the product of the yeast HIS3 gene another IGPD, e.g. in the yeast two-hybrid system.

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