Relationship among the genes, enzymes, and intermediates of the biosynthetic pathway of lysine in Saccharomyces

Summary Genetic lesions of 10 of the lysine loci in Saccharomyces have been provisionally correlated with the various enzymatic steps of the homocitric acid pathway for the biosynthesis of lysine. The characterization of mutational blocks in different mutants was made on the basis of the accumulation of appropriate intermediates, lack of enzymatic activity, and feeding experiments. Genetic lesions in mutants lys ₄, lys₇, lys₈, and lys ₁₂ correspond to the biochemical steps between homocitric acid and -amino-adipic acid. Similarly the genetic lesions in lys ₁, lys₂, lys₅, lys₉, lys₁₃, and lys ₁₄ correspond to the intermediate steps between -aminoadipic acid and lysine. Lysine-genes are not clustered, instead are mapped on different chromosomes of Saccharomyces. Some of the intermediate steps in the biosynthesis of lysine correspond to two or more unlinked genes.Supported by NSF Grant GB 28558X, Lilly Research Foundation, and Faculty Research Committee, Miami University.