Abstract
D-Tryptophan and l-tryptophan are accumulated by cells of a species of Flavobacterium via the same or similar transport systems. The accumulation of both tryptophan isomers is inhibited by 2,4-dinitrophenol. D-Tryptophan inhibits the accumulation of l-[ 14C]tryptophan by a washed cell suspension whereas the uptake of d-[ 14C]tryptophan is reduced in the presence of l-tryptophan. Thus, the tryptophan transport system does not exhibit the stereospecificity characteristic of certain other amino acid transport mechanisms. The accumulation of both d-[ 14C]-tryptophan and l-[ 14C]tryptophan by a washed cell suspension is readily inhibited by l-5-hydroxytryptophan, and and dl-tryptazan, slightly inhibited by d-5-hydroxytryptophan, and insensitive to the concentration of tryptamine used in this investigation. Tryptophol showed a more pronounced inhibition of the accumulation of l-tryptophan than was observed when d-tryptophan was the substrate. The oxidative dissimilation of d-tryptophan by a cell extract is influenced by several tryptophan analogs. Tryptophol, tryptamine, dl-tryptazan, and l-5-hydroxytryptophan inhibit oxidation of d-tryptophan by the enzyme-containing extract using 2,6-dichlorophenolindophenol as the electron acceptor.
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