Mutants of the methylotrophic yeast Pichia pinus defective in C sub(2) metabolism

A collection of mutants of Pichia pinus which are unable to grow on ethanol but retain the ability to grow on glucose and methanol, was obtained. Genetic biochemical analysis of these strains revealed mutations in seven nuclear genes affecting activities of isocitrate lyase (icl1 ), malate synthase (mls1 ), phosphoenolpyruvate carboxykinase (pck1 ), "malic" enzyme (mdd1 ) and acetyl-CoA synthetase (acs1, acs2 and acs3 ). All mutations except acs1-acs3 have no effect on the activities of other enzymes involved in C sub(2) metabolism. Mutations acs1, acs2 and acs3 have a pleiotropic action, leading to partial reduction in activities of isocitrate lyase and malate synthase.