GTP Cyclohydrolase 1

**Semantic type:** Amino Acid, Peptide, or Protein|Enzyme

**Definition:** GTP cyclohydrolase 1 (250 aa, ~28 kDa) is encoded by the human GCH1 gene. This protein is involved in the conversion of GTP to D-erythro-7,8-dihydroneopterin triphosphate, which is the first step in tetrahydrobiopterin (BH4) synthesis.

**Synonyms:** - EC 3.5.4.16 - GCH1 - GTP Cyclohydrolase I - GTP-CH-I - Guanosine 5'-Triphosphate Cyclohydrolase I