IMP cyclohydrolase


In enzymology, an IMP cyclohydrolase is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are IMP and H2O, whereas its product is 5-formamido-1-imidazole-4-carboxamide.
This enzyme belongs to the family of hydrolases, those acting on carbon-nitrogen bonds other than peptide bonds, specifically in cyclic amidines. The systematic name of this enzyme class is IMP 1,2-hydrolase . Other names in common use include inosinicase, and inosinate cyclohydrolase. This enzyme
catalyses the cyclisation of 5-formylamidoimidazole-4-carboxamide ribonucleotide to IMP, a reaction which is important in de novo purine biosynthesis in archaeal species.

Structural studies

In most cases this single-domain protein is arranged to form an overall fold that consists of a four-layered alpha-beta-beta-alpha core structure. The two antiparallel beta-sheets pack against each other and are covered by alpha-helices on one face of the molecule. The protein is structurally similar to members of the N-terminal nucleophile hydrolase superfamily. A deep pocket was in fact found on the surface of IMP cyclohydrolase in a position equivalent to that of active sites of NTN-hydrolases, but an N-terminal nucleophile could not be found. Therefore, it is thought that this enzyme is structurally but not functionally similar to members of the NTN-hydrolase family.
As of late 2007, 14 structures have been solved for this class of enzymes, with PDB accession codes,,,,,,,,,,,,, and.