28 yeast strains comprising a number of genera and species have been studied with respect to their ability to use L-lysine as carbon or nitrogen source. Based on the utilization of this amino acid we could separate the yeasts into 3 groups. Enzymatic investigations demonstrate that yeasts can degrade L-lysine by two distinct pathways. The first step of both ways was investigated and it was demonstrated that 3 enzymes, acetyl-CoA : L-lysine N-acetyltrdnSferdSe, L-lysine e-aminotransferase, L-lysine Edehydrogenase, are able to catalyze the initial reaction. In 9 yeast strains the acetyltransferase was found. In 21 strains the aminotransferase and in 2 species the dehydrogenage could be detected. The enzyme formation could be enhanced in cells grown in the presence of L-lysine as sole carbon and/or as sole nitrogen source. ") Growth was determined by the difference of OD,,, after 30 h of incubation and before incubation b, Yeasts were grown in minimal medium ' ) Yeasts were grown in medium containing L-lysine as sole nitrogen source d, Yeasts were grown in medium containing L-lysine as sole carbon source Candida nitratophila SBUG 540 4.0 4.0 0.0 Candida tropicalis SBUG 590 10.2 10.0 8.4