Guanosine triphosphate cyclohydrolase I (GTPCH or GCH1)

Guanosine triphosphate cyclohydrolase I (GTPCH, also known as GCH1) is a key enzyme that catalyzes the first and rate-limiting step in the biosynthesis of tetrahydrobiopterin (BH4), an essential cofactor for aromatic amino acid hydroxylases involved in the production of neurotransmitters (dopamine, norepinephrine, epinephrine, serotonin), as well as nitric oxide synthases. The enzyme is a homodecamer with a toroidal structure, and its activity is crucial for brain and endothelial function. Mutations in the GCH1 gene are associated with autosomal dominant and recessive forms of GTP cyclohydrolase I deficiency, resulting in clinical conditions such as dopamine-responsive dystonia, hyperphenylalaninemia, and neurological disorders. GTPCH can be targeted pharmacologically (e.g., by sapropterin in BH4 deficiency syndromes), and inhibitors like DAHP have been used experimentally. The enzyme is considered a validated therapeutic target in metabolic and neurological disease contexts[1][2][3][4][5][6].

Other names

GTP cyclohydrolase IGCH1GTPCHGTP-CH-I

Drugs targeting GTP cyclohydrolase I can act via enzyme inhibition (small molecules or synthetic derivatives can inhibit GTP cyclohydrolase I to reduce tetrahydrobiopterin levels) or through enzyme replacement/augmentation (e.g., sapropterin acts as a cofactor supplement).