GTP cyclohydrolase I ( GTPCH) ( EC 18.104.22.168) is a member of the GTP cyclohydrolase family of enzymes. GTPCH is part of the folate and biopterin biosynthesis pathways. It is responsible for the hydrolysis of guanosine triphosphate (GTP) to form 7,8-dihydroneopterin 3'-triphosphate (7,8-DHNP-3'-TP, 7,8-NH 2-3'-TP).
encoded by the gene GCH1. Several alternatively spliced transcript variants encoding different isoforms have been described; however, not all of the variants give rise to a functional enzyme. [1 ]
Clinical significance [ edit ]
Mutations in this gene are associated with malignant phenylketonuria (PKU) and hyperphenylalaninemia (HPA), as well as L-DOPA (Levodopa)-responsive dystonia. [1 ]
Function [ edit ]
transcribed protein is the first and rate-limiting enzyme in tetrahydrobiopterin (THB, BH 4) biosynthesis, catalyzing the conversion of GTP into 7,8-DHNP-3'-TP. THB is an essential cofactor required by the aromatic amino acid hydroxylase (AAAH) and nitric oxide synthase (NOS) enzymes in the biosynthesis of the monoamine neurotransmitters serotonin (5-hydroxytryptamine (5-HT)), melatonin, dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), and nitric oxide (NO), respectively.
See also [ edit ]
References [ edit ]
Further reading [ edit ]
Voet, Judith G.; Voet, Donald (2004). Biochemistry. New York: J. Wiley & Sons. ISBN 0-471-39223-5.
External links [ edit ]
1fb1: CRYSTAL STRUCTURE OF HUMAN GTP CYCLOHYDROLASE I
1is7: Crystal structure of rat GTPCHI/GFRP stimulatory complex
1is8: Crystal structure of rat GTPCHI/GFRP stimulatory complex plus Zn
1wpl: Crystal structure of the inhibitory form of rat GTP cyclohydrolase I/GFRP complex