MULTIPLE MOLECULAR-FORMS OF ALCOHOL OXIDASE FROM THE METHYLOTROPHIC YEAST PICHIA-METHANOLICA

Alcohol oxidase (AO) isolated from Pichia methanolica MH4 exists in ni ne molecular forms. A combination of ion-exchange high-performance liq uid chromatography (HPLC) and preparative electrophoresis under nonden aturing conditions resulted in isolation, purification, and partial ch aracterization of individual AO forms displaying equal molecular weigh ts but different pI(5.2-4.2), the K-m for methanol (0.5-6.5 mM), and t he contents of mFAD (78.7-1 8.1%). The ratio of relative levels of the se isoforms was an important feature that consistently changed in cons ecutive phases of the culture growth and upon changes in the growth ra te in the chemostat mode. The isoform displaying the highest electroph oretic mobility dominated at the beginning of exponential growth durin g periodic cultivation and at high growth rates during cultivation in a chemostat, whereas the low-mobility isoform was mainly found in the late stationary phase and at low growth rates during chemostat cultiva tion. Mechanisms that can mediate the formation of multiple forms of A O and their functional roles are discussed.