Thermal inactivation of maltase and its application to temperature-sensitive mutants of yeast.

Three maltases have been detected in each of a variety of strains of Saccharomyces. These are present in constant relative amounts in a particular strain and are characterized by reproducible first order thermal decay constants. Four of six mutants, temperature-sensitive for maltose fermentation, lack the maltase of intermediate stability. This deficiency appears to be the basis of the temperature sensitivity, and it is concluded that these strains carry a mutation in the structural gene for that maltase.