Conditions for the production of tryptophanase from Achromobacter liquidum and for the conversion of l-serine and indole to l-tryptophan were studied. The enzyme could be produced in amounts as great as 0.750 U/ml (degradation) and 0.294 U/ml (synthesis) by shaking cultures at 30 degrees C in a medium containing dextrin, yeast extract, l-tryptophan, and l-glutamic acid. l-Tryptophan was produce...

Indoleamine 2,3-dioxygenase (IDO) has been identified as an important antimicrobial and immunoregulatory effector molecule essential for the establishment of tolerance by regulating local tryptophan (Trp) concentrations. On the other hand, the immunosuppressive capacity of IDO can have detrimental effects for the host as it can lead to deleterious alterations of the immune response by promoting...

The process of induction of tryptophan oxygenase in Pseudomonas acidovorans is typical of many microbial enzyme induction systems, in that it (i) requires cell multiplication and de novo protein synthesis, (ii) is subject to catabolite repression, (iii) results in the formation of a stable enzyme, whose level, upon removal of inducer, is diluted out by cell proliferation, and (iv) exhibits prod...

The possible functional significance of induction of the hepatic enzymes, tryptophan pyrrolase and tyrosine transaminase, has been studied in intact normal and adrenalectomized adult male rats and in the isolated perfused rat liver. In intact, normal rats, several-fold increases in tryptophan pyrrolase activity induced by treatment with hydrocortisone or tryptophan, or both, were associated wit...

Twenty six Rhizobium strains were isolated from root nodules of Sesbania sesban (L.) Merr. collected from different regions of Andhra Pradesh. All the 26 Rhizobium strains produced indole acetic acid (IAA), but maximum amount was produced by only five strains in yeast extract mannitol  (YEM) medium supplemented with L-tryptophan. The strains were found to elaborate maximum IAA when fed with 2.5...

The possible functional significance of induction of the hepatic enzymes, tryptophan pyrrolase and tyrosine transaminase, has been studied in intact normal and adrenalectomized adult male rats and in the isolated perfused rat liver. In intact, normal rats, several-fold increases in tryptophan pyrrolase activity induced by treatment with hydrocortisone or tryptophan, or both, were associated wit...

Intraruminal doses of L-tryptophan cause acute pulmonary edema and emphysema in cattle. The D and L isomers of tryptophan and 22 related indolic compounds were incubated with ruminal microorganisms in vitro. Incubation of L-[U-benzene ring-(14)C]tryptophan with ruminal microorganisms for 24 h resulted in 39% of the added radioactivity being incorporated into skatole, 7% into indole, and 4% into...

IDO is the rate-limiting enzyme in the kynurenine pathway, catabolizing tryptophan to kynurenine. Tryptophan depletion by IDO-expressing tumors is a common mechanism of immune evasion inducing regulatory T cells and inhibiting effector T cells. Because mammalian cells cannot synthesize tryptophan, it remains unclear how IDO(+) tumor cells overcome the detrimental effects of local tryptophan dep...

Tryptophanase, L-tryptophan indole-lyase with extremely absolute stereospecificity, can change the stereospecificity in concentrated diammonium hydrogenphosphate solution. While tryptophanase is not inert to D-serine in the absence of diammonium hydrogenphosphate, it can undergo L-tryptophan synthesis from D-serine along with indole in the presence of it. It has been well known that tryptophana...

Ferrous L-tryptophan-2,3-dioxygenase reacts with nitric oxide both in the presence and in the absence of L-tryptophan. Electron paramagnetic resonance studies suggest that the proximal ligand of the heme is a nitrogen atom, probably from an histidyl residue. The interaction of the protein with substrate changes both the symmetry of the paramagnetic center and the mode of interaction of the iron...