The first and rate limiting step in serotonin (5-HT) biosynthesis is catalyzed by tryptophan hydroxylase. The enzyme requires iron(II), tetrahydrobiopterin, and dioxygen cofactors for the hydroxylation of L-tryptophan to 5-hydroxytryptophan. Tryptophan hydroxylase belongs to a small family of monooxygenases that utilize tetrahydrobiopterins. Other members are phenylalanine hydroxylase and tyrosine hydroxylase (Fitzpatrick, PF, 1999; Walther et al, 2003).
Haavik, J, Erlandsen, H, Knappskog, PM, Wang, L, Stevens, RC
Hörtnagl, H, Walther, DJ, Fink, H, Bashammakh, S, Voits, M, Bader, M, Peter, JU
tryptophan 5-monooxygenase activity of TPH:Fe++ [cytosol]
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