Metabolic Fates of L-Tryptophan in Saccharomyces uvarum : Saccharomyces carlsbergensis

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The metabolism of L-tryptophan by Saccharomyces uvarum (carlsbergensis) was investigated by simultaneous measuring of fluxes through kynureinase, through transaminases and into protein using L-[methylene ^<14>C]-and L-[side chain-2,3-^3H]tryptophan. In yeast cultivated in synthetic medium (S medium), the flux into protein was predominant, closely followed by the flux leading to 2-^3H liberation. The proportion of L-tryptophan metabolized via the latter fluxincreased over 10-fold (75% of total tryptophan metabolized) as the concentration of L-tryptophan was raised from 5×10^<-5> to 5×10^<-4>M. L-Tryptophan metabolized via the kynureninase flux was less than 5% of total tryptophan metabolized. In yeast extract-polypepton-glucose medium (YPG medium), more tryptophan was incoporated into protein than in the S medium. Contribution of the kynureninase flux remained very low. Tryptophan metabolism via each flux changed depending on the growth phase. 2-^3H liberation was shown to be primarily due to tryptophol synthesis by high performance liquid chromatography (HPLC) and nuclear magnetic resonance (NMR), indole-3-acetic acid and kynurenic acid also contributing to 2-^3H liberation but to a much lesser extent. 2-^3H liberation increased dose-dependently at tryptophan concentration higher than 10^<-5>M, while the kynureninase flux reached its plateau at 10^<-5>M. Formation of tryptophol and indole-3-acetic acid via indole-3-pyruvic acid and indole-3-acetaldehyde with indole aldehyde as a by-product was confirmed using exogenous tryptophan metabolites with indole rings.
社団法人日本薬学会の論文
1991-07-25

Metabolic Fates of L-Tryptophan in Saccharomyces uvarum : Saccharomyces carlsbergensis

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