d-Tryptophan was converted to l-tryptophan in tissue cultures of tobacco, in whole cells treated with dimethylsulfoxide, and in cell-free extracts treated by Sephadex G-25 filtration. Evidence was obtained that tryptophanase, tryptophan pyrrolase, and transaminase activities were not involved. The data were best explained by the presence of a tryptophan racemase as the enzyme catalyzing the rea...

HIV-1-infected patients have low circulating tryptophan concentrations despite evidence of adequate dietary intake of this essential amino acid. A chronic increase in inducible tryptophan oxidation is the basis of HIV-1-associated tryptophan depletion. This metabolic process results in the irretrievable loss of tryptophan molecules from the available pool. Such sustained disruption of normal tr...

L-Tryptophan-2,3-dioxygenases (EC 1.13.1.12), purified to homogeneity from Pseudomonas acidovorans and from rat liver, have been shown to contain as bound cofactors, 2 g atoms copper and 2 moles of heme per mole of tetrameric enzyme. Kinetic and spectral studies, utilizing the metal complexing agents diethyldithiocarbamate (Cu2+ specific), bathocuproinesulfonate (Cu+ specific), and bathophenant...

Fernstrom & Wurtman (1971) showed that re-feeding starved rats with a protein-free meal led to a rise in brain tryptophan and 5-hydroxytryptamine concentrations, and an increase in the total serum tryptophan. The rate-limiting factor in brain S-hydroxytryptamine synthesis is considered to be the availability of tryptophan in the brain; this in turn is regulated, not by the total serum tryptopha...

Tryptophan catabolism via the enzyme indoleamine 2,3-dioxygenase (IDO) allows human monocyte-derived macrophages (MDM) and other APC to suppress T cell proliferation. IDO helps protect murine fetuses from rejection by the maternal immune system and can promote tolerance and immunosuppression. For tryptophan to be catabolized by IDO, it must first enter the APC via transmembrane transport. It ha...

A systematic study of the modification of papain (its thiol group protected as a disulphide with mercaptoethanol) by N-bromosuccinimide, showed that 2 molar equiv. modified tryptophan-69 and 4 molar equiv. modified tryptophan-69 and -177. The Michaelis parameters for the catalysed hydrolysis of N-benzyloxycarbonylglycine p-nitrophenyl ester by these modified enzymes were determined. The enzymic...

The metabolism of L-tryptophan by isolated liver cells prepared from control, adrenalectomized, glucocorticoid-treated, acute-diabetic, chronic-diabetic and insulin-treated chronic-diabetic rats was studied. Liver cells from adrenalectomized rats metabolized tryptophan at rates comparable with the minimum diurnal rates of controls, but different from rates determined for cells from control rats...

To seek novel antitumor agents, we designed and synthesized new 1-tryptophan analogs based on tryptophan catabolism. 1-Alkyl-tryptophan analogues including 1-ethyltryptophan (1-ET), 1-propyltryptophan (1-PT), 1-isopropyltryptophan (1-isoPT) and 1-butyltryptophan (1-BT) were synthesized from tryptophan. We examined whether those compounds had the antiproliferative effects on SGC7901 and HeLa cel...

The various calorimetric methods now employed for the estimation of tryptophan are not specific for tryptophan but give colored products with many compounds containing the indole nucleus, including indole itself. In order to facilitate studies of the enzymatic synthesis of tryptophan from indole and serine by extracts of Neurospora (l), a search for a rapid, quantitative method for the estimati...

By using an antiserum raised against rat liver tyrosine aminotransferase, it was shown that about 60% of tryptophan aminotransferase activity in rat liver extracts is catalysed by this enzyme. Induction of tryptophan aminotransferase activity by intraperitoneal injections of tryptophan or triamcinolone can be entirely attributed to the effects of these agents on tyrosine aminotransferase. The o...