GTP-Cyclohydrolase I

• OMIM: 600225
• UniProt: P30793

GTP cyclohydrolase I ( GCH1 ) is the name for the enzyme which breaks down to a GTP precursor of biopterin and is thus involved in the formation of biopterin, a coenzyme. Variants of the enzyme exists in many living beings and in humans are four isoforms known, of which only an enzymatic activity. Mutations in the GCH1 gene, can cause atypical, severe form of phenylketonuria and a form of dystonia that is treatable with DOPA.

Catalyzed reaction

GCH1 is responsible for the hydrolysis of guanosine triphosphate (GTP), from which it formed a degradation product by the catalytic reactions of three, which is converted to tetrahydrobiopterin by two additional enzymes.