Protogen and its Relation to Ketoacids in Metabolism of Tetrahymena.

Abstract

T. geleii in acetate-free, protogen-deficient media grows to a limited extent and then dies. Death is due to a fall in the pH of the medium to about 4.0. The acids accumulated consist mainly of pyruvic and alpha-ketoglutaric acids, as judged tentatively by the use of paper chromatography, differential solubility and spectral absorption of the 2,4-dinitrophenyl hydrazones of the keto-acids. Protogen (thioctic acid) is required for the oxidative decarboxylation of alpha-ketoglutaric acid as well as for oxidation of pyruvic acid. An additional function in the metabolism of T. geleii is postulated.