Application of chromatography. XXX. Studies on tryptophan metabolism in the culture of Eremothecium ashbyii.

Abstract

In isolating a green fluorescent substance (G compound) from the mycelium of Er. ashbyii, yellow crystals, m.p. 223∼224°(decomp.), [α]20D-43.2°, were also separated and this substance was established as l-3-hydroxykynurenine. Study of the mycelium and broth of Er. ashbyii by two-dimentional paper chromatography detected only tryptophan and l-hydroxykynurenine as amino acid of tryptophan series, kynurenine being never detected. The two compounds were found from a comparatively early stage of the culture and they were readily distinguished by the color reaction with p-dimethy1-aminobenzaldehyde (Ehrlich reagent). Formation of riboflavin, l-hydroxykynurenine, and nicotinic acid was also investigated at intervals during the culture and it was found that riboflavin increased in proportion to the increase of l-hydroxykynurenine, but the formation of nicotinic acid factor seemed to have no quantitative relation to them. A leuco strain of Er. ashbyii obtained by successive culture of the yellow strain was also cultivated on the same medium and it was found that in addition to a slightly smaller production of the mycelium, the production of riboflavin and l-hydroxykynurenine was extremely low, compared with their production in the yellow strain. From such a fact it was presumed that the metabolism of kynurenine to l-hydroxykynurenine in the yellow strain is very active and that this oxidative process in the living body requires a large quantity of riboflavin.