Régulations métaboliques de la biosynthèse de la méthionine et de la thréonine chez Saccharomyces cerevisiae

The kinetic of synthesis of the first enzymes of the part of pathway common to threonine and methionine synthesis in Saccharomyces cerevisiae have been studied, under conditions of repression followed by depression. The results show that repression is established immediately and that enzyme synthesis continues at a constant rate, whereas derepression is established slowly and progressively.

These results are in agreement with the hypothesis of a rapid transformation of exogenous repressor (end-product amino acid) into “endogenous repressor”. The slow elimination of the latter is probably due to temporary maintenance of exogenous repressoe in the amino acid pool of the cells.