Imidazoleglycerol-phosphate dehydratase

In enzymology, an imidazoleglycerol-phosphate dehydratase (EC 4.2.1.19) is an enzyme that catalyzes the chemical reaction

D-erythro-1-(imidazol-4-yl)glycerol 3-phosphate 3-(imidazol-4-yl)-2-oxopropyl phosphate + H₂O

Hence, this enzyme has one substrate, D-erythro-1-(imidazol-4-yl)glycerol 3-phosphate, and two products, 3-(imidazol-4-yl)-2-oxopropyl phosphate and H₂O. This reaction is the seventh 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-yl)glycerol-3-phosphate hydro-lyase [3-(imidazol-4-yl)-2-oxopropyl-phosphate-forming]. Other names in common use include IGP dehydratase, and D-erythro-1-(imidazol-4-yl)glycerol 3-phosphate hydro-lyase. This enzyme participates in histidine metabolismas it is involved in the 6th step of histidine biosynthesis as part of a nine step cyclical pathway.

IGPD is a recognised novel herbicide target as animals do not have an IGPD

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.^[1] In E. coli, this is the protein encoded by the hisB gene.^[2]

Structural studies

As of late 2007, 3 structures have been solved for this class of enzymes, with PDB accession codes 1RHY, 2AE8, and 2F1D.

References

Further reading

• AMES BN (1957). "The biosynthesis of histidine; D-erythro-imidazoleglycerol phosphate dehydrase". J. Biol. Chem. 228 (1): 131–43. PMID 13475302.