ISOZYMES OF METHANOL OXIDASE IN A METHANOL-UTILIZING YEAST, PICHIA-METHANOLICA IAM-12901

Methanol oxidases (MODs) were investigated in some methanol-utilizing yeasts. Pichia methanolica IAM 12901 and IAM 12481 (= Pichia cellobios a) produced 9 forms of methanol oxidase on electrophoresis when grown on methanol but 1 form when grown on glycerol or pectin. Other strains -Candida boidinii IAM 12875, Pichia angusta IAM 12897, and Pichia past oris IAM 12903-produced one band on electrophoresis when grown on meth anol. Methanol oxidases with the smallest and largest Pm (relative mob ility)-MOD A and MOD B-were purified from methanol-grown cells; anothe r methanol oxidase (MOD P) was purified from pectin-grown cells of P. methanolica IAM 12901. All the purified enzymes were octamers composed of subunits with a molecular mass of 70,000 Da. MOD A and MOD P were mostly identical with each other in terms of their enzymatic character istics, but MOD B differed from the other two with respect to substrat e specificity, the prosthetic group, and the apparent K-m for methanol . Southern analysis of the genomic DNA of P. methanolica LAM 12901 was carried out with the partial methanol oxidase gene as a probe. The ge nomic DNA of this yeast showed the presence of 2 methanol oxidase gene s. It was concluded that the 9 forms of MOD in P. methanolica were iso zymes of a chimera octamer consisting of 2 subunits encoded by differe nt methanol oxidase genes.