SUMMARY: Y185, grown anaerobically in media containing ergosterol and palmitoleic, oleic or linoleic acids, synthesized phospholipids extensively enriched in the exogenously supplied fatty acid. A study was made of the effect of solute concentration on rates of accumulation of nine amino acids by organisms enriched in different fatty-acyl residues. Data were fitted using computer-aided statistical analysis to three equations to derive kinetic constants for accumulation. Analysis of data for two of the amino acids, namely L-threonine and L-histidine, showed different kinetics in organisms enriched in different fatty-acyl residues. Woolf-Hofstee plots for accumulation of L-threonine, as well as L-serine, showed abrupt changes in curvature at low concentrations with differently enriched organisms. Data for accumulation of both amino acids gave a significant fit to the model describing accumulation by one transport system without diffusion. Data for accumulation of L-histidine as well as L-aspartic acid best fitted a model describing accumulation by one transport system and diffusion. Values for and the diffusion constant, but not , differed only for accumulation of L-histidine in organisms with different fatty-acyl enrichments. A third model, describing accumulation by two separable transport systems, best fitted data for accumulation of L-glutamic acid and L-methionine. Data for accumulation of L-leucine, L-isoleucine and L-valine could not be fitted to any of the models. Woolf-Hofstee plots for accumulation of L-leucine and L-isoleucine by organisms enriched in oleyl or linoleyl residues were superimposable, although similar plots for accumulation of L-valine differed in shape.


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