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Importance of tryptophan pyrrolase and aromatic amino acid decarboxylase in the catabolism of tryptophan


, : Importance of tryptophan pyrrolase and aromatic amino acid decarboxylase in the catabolism of tryptophan. Biochemical Pharmacology 27(5): 763-767

Benserazide, an inhibitor of aromatic amino acid decarboxylase, potentiates the rise of plasma tryptophan in rats given a tryptophan load. It also inhibits 14CO2 release from animals given carboxyl-labeled tryptophan. These results are explained by the ability of benserazide to inhibit tryptophan pyrrolase, the most important enzyme catabolizing tryptophan. Direct decarboxylation is not a quantitatively important pathway of tryptophan catabolism and carboxyl-labeled tryptophan is metabolized to 14CO2 primary by the pyrrolase pathway. These data have implications for the clinical use of tryptophan as an antidepressant. Pyridoxine, which is often given with tryptophan in clinical use, can activate aromatic amino acid decarboxylase. Pyridoxine does not inhibit the rise of plasma tryptophan in rats given a tryptophan load and is unlikely to antagonize the therapeutic effect of tryptophan. It may be possible to potentiate the therapeutic effect of tryptophan by administering it with benserazide to inhibit its peripheral catabolism through the pyrrolase pathway.

US$19.90

PMID: 77669

DOI: 10.1016/0006-2952(78)90517-8


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