Methionine biosynthesis in Saccharomyces cerevisiae. II. Gene-enzyme relationships in the sulfate assimilation pathway.

In Saccharomyces cerevisiae, the products of eleven different genes are needed for a functional sulfate assimilation pathway. Only five enzymatic steps are known in this pathway. The study of the gene-enzyme relationships has shown that the enzymes catalysing two of these steps are probably heteropolymeric. Moreover, mutations in three unlinked genes lead to multiple enzymatic losses. Different hypotheses are made to account for these results.