Induction and genetics of two alpha-galactosidase activities in Saccharomyces cerevisiae

The induction of alpha-galactosidase of Saccharomyces cerevisiae was investigated. We have demonstrated the existence of inducible internal and external alpha-galactosidase activities and have studied the relationship between the two alpha-galactosidases by examining a mutant strain which lacks both the internal and external activities. The mutant possesses a mutation in a single locus (mel1-1) which does not affect the synthesis of the other galactose pathway enzymes or the ability of the yeast to grow on media containing only galactose as the carbon source. Genetic studies of the mutant indicate that mel 1-1 is recessive and allelic to the wild tye allele for melibiose fermentation Mel 1.