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In enzymology, an IMP cyclohydrolase () is an enzyme that catalyzes the chemical reaction :IMP + H2O 5-formamido-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide Thus, the two substrates of this enzyme are IMP and H2O, whereas its product is 5-formamido-1-(5-phospho-D-ribosyl)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 (decyclizing). 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 (NTN) 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 . 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IMP cyclohydrolase」の詳細全文を読む スポンサード リンク
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