Glucosamine-resistant mutations in yeast affecting the glucose repression sensitivity of electron transport enzymes

We have isolated two mutant strains, GSA(r)-4 and GSA(r)-5, which are able to grow on lactate in the presence of D-glucosamine. The glucosamine-resistant phenotype results from the cooperative effects of mutations in three loci, GAR1, GAR2 and GAR3. Both glucosamine resistant mutant strains were doubly mutant at gar1 gar2 (GSA(r)-4) or gar1 gar3 (GSA(r)-5). The mutants were also shown to exhibit glucose repression insensitive synthesis of NADH-cytochrome c reductase and cytochrome c oxidase. Glucose-repressible synthesis of the following enzymes was seen: succinic dehydrogenase, succinic: cytochrome c reductase, maltase (PNPGase), galactokinase, α-galactokinase. The glucose-repression insensitivity segregates in association with the glucosamine resistance.