Genetic and biochemical studies of phosphomannose isomerase deficient mutants of Saccharomyces cerevisiae.

Three mannose-negative mutants of Saccharomyces cerevisiae have been isolated. These mutants showed growth inhibition when mannose was added to a growth medium containing glycerol or fructose. Crosses between wild type mutants showed segregation of 2+/2-. Crosses between the mutants themselves showed that they were closely linked. Two mutants (XM3 and D2) showed characteristics of allelic structural alteration of phosphomannoseisomerase. Mutant D4 had a deficiency of phosphomannoseisomerase activity, but with a normal thermostability. Revertants from D4 had a normal thermostability.