7-Hydroxytryptophan (7-HTP) is a non-proteinogenic amino acid. It is also a 5-hydroxytryptophan (5-HTP) positional isomer, a L-tryptophan derivative, structurally belonging to the hydroxytryptophan family, and a substituted tryptophan with a hydroxyl group at position 7 of the indole ring. It is not a precursor of serotonin. 7-Hydroxytryptophan is a metabolite detected in human urine.
It has been investigated for its role as a precursor in melanin-related oxidative processes.
7-Hydroxytryptophan is found in human urine, but its formation pathway in the body is unknown.
Natural occurrence 7-Hydroxytryptophan is present in the mussel adhesive protein Pvfp-1 of Perna viridis as a post-translationally modified tryptophan residue. This modified residue exhibits redox activity, potentially substituting for DOPA.
7-Hydroxytryptophan was first identified in fungi and was isolated from the fruiting bodies of the fungus Cortinarius purpurascens, where it can serve as a precursor for the synthesis of azepino-indole alkaloids (so-called purpurascenins A–C) via the Pictet–Spengler reaction.
7-Hydroxytryptophan in archaea 7-hydroxytryptophan has been identified as a rare post-translational modification in the active site of the enzyme MCR (methyl-coenzyme M reductase) in methanotrophic archaea (ANME-MCR group) But the role of ANME is assumed to be that 7-hydroxytryptophan compensates for the lack of arginine methylation.
Metabolism In normal tissues, 7-HTP either remains metabolically inactive or is incorporated into normal amino acid metabolism pathways without the formation of toxic products.
In tumor cells expressing tryptophan hydroxylase, 7-hydroxytryptophan is enzymatically converted in situ into the toxic compound 5,7-dihydroxytryptamine (5,7-DHT). This metabolite induces apoptosis selectively in serotonin-producing tumor cells. And also interferes with the autocrine ability to synthesize serotonin. The conversion of 7-HTP to 5,7-DHT is completely inhibited by the specific tryptophan hydroxylase inhibitor para-chlorophenylalanine (Fenclonine).
Pharmacology Oxidase from the gill plates of mussels (Mytilus edulis) is able to oxidize 7-Hydroxytryptophan and other related compounds, whereas mammalian ceruloplasmin has almost no effect on the compounds.
See also 5,7-dihydroxytryptamine 5-Hydroxytryptophan Tryptophan hydroxylase Post-translational modification
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