Déficience en cytochrome oxydase chez les souches de <em>Saccharomyces cerevisiae</em> exigeant la tréonine pour leur croissance.

In the previous paper, a metabolic relationship between a cytochrome oxidase deficiency and threonine biosynthesis in Saccharomyces cerevisiae was proposed. It has been found that high concentrations of threonine or its immediate precursors L-aspartate- β-semi-aldehyde or homoserine, are able to restore cytochrome oxidase synthesis in threonine auxotrophs, grown in the presence of glucose as a carbon source. On the other hand, these strains are able to synthesize cytochrome oxidase when the carbon source is ethanol or glycerol even without an excess of threonine. The results show that this phenomenon is concerned with the regulation of cytochrome oxidase synthesis. Different hypotheses are presented to explain the possible role of threonine in this regulation. One of them stresses the possible role of a differential auxotrophy for the cytoplasmic and the mitochondrial protein synthesis systems. [ABSTRACT FROM AUTHOR]