Tryptophan hydroxylase 1 is a human gene encoded by the symbol, TPH1. It may also be known as: Tryptophan 5-hydroxylase 1; Tryptophan 5-hydroxylase 1 ; Tryptophan 5-monooxygenase 1; TPRH; TRPH. The encoded protein is an enzyme with an amino acid length of 444 and a mass of 51.0 kDa. Other isoforms may exist. Tryptophan hydroxylase 1 is a member of the Biopterin-dependent aromatic amino acid hydroxylase family. Homologs of this gene exist in other organisms, including: Mouse, Fly, Rat, Zebrafish.