The effects of three different mal loci on the regulation of maltase synthesis in yeast.

Inbred haploid strains of Saccharomyces cerevisiae carrying MAL1, MAL2 or MAL6 in a common background have been crossed to each other and to strains carrying no active MAL loci. The kinetics of maltase induction and the induced maltase levels have been examined in the inbred strains and in haploid segregants of the crosses. Differences have been found in the kinetics of induction and induced maltase levels that segregate with the different MAL loci. In the strains tested, the relative rates of maltase induction were MAL2 greater than MAL6 much greater than MAL1; the relative induced maltase levels were MAL2 greater than MAL6 similar to MAL1. These results indicate that MAL1, MAL2 and MAL6 are (or include) regulatory genes that control the accumulation of the enzymes of maltose fermentation.