Mutations affecting the enzymes involved in the utilization of 4-aminobutyric acid as nitrogen source by the yeast Saccharomyces cerevisiae

We present genetic evidence for the enzymes 4‐aminobutyrate: 2‐oxoglutarate aminotransferase (EC 2.6.1.19) and succinate‐semialdehyde dehydrogenase [NAD(P)+] (EC 1.2.1.16) constituting the functional pathway for the utilization of 4‐aminobutyric acid as a nitrogen source by Saccharomyces cerevisiae. We show that the pathway is induced by 4‐aminobutyric acid and that the presence of the pathway enzymes probably requires the integrity of a positive control element.