Function
Cyclohydrolase is an enzyme which catalyzes the reversible cyclization or the ring opening of a purine ring.
• GTP cyclohydrolase I catalyzes the conversion of GTP to 7,8-dihydronepterin triphosphate. GCH I is part of the folate and biopterin biosynthesis[1]
• GTP cyclohydrolase II catalyzes the conversion of GTP to formate, diphosphate and diamino-hydroxy-phosphoribosylamino pyrimidine. GCH II is part of riboflavin metabolism.[2]
• IMP cyclohydrolase catalyzes the conversion of IMP to formido-phosphosibosyl imidazole carboxamide. ICH is part of the purine biosynthesis[3] See also Bifunctional purine biosynthesis protein PURH.
• Methenyltetrahydromethanopterin cyclohydrolase catalyzes the conversion of methenyltetrahydromethanopterin to formyl-tetrahydromethanopterin. MCH is part of the folate biosynthesis[4]
- Methylenetetrahydrofolate dehydrogenase/cyclohydrolase catalyzes the interconversion of 5,10-methylenetetrahydrofolate and 10-formyltetrahydrofolate in mitochondria of mammalian cells.[5]
- Phosphoribosyl AMP-cyclohydrolase catalyzes the third step of His biosynthesis.[6]
Disease
Mutations in GTP cyclohydrolase I are associated with malignant phenylketonuria, hyperphenylalaninemia and DOPA-responsive dystonia.
Structural highlights
from Escherichia coli (1n3r) is pentamer. at the intersubunit interface.[7] .
3D structures of cyclohydrolase
Cyclohydrolase 3D structures