Metabolic Regulation in Methylotrophic Yeasts

Abstract

The ability to grow in media containing methanol (the C1 substrate predominantly used as a carbon-and energy source) is not nearly as widespread among yeasts as it is in bacteria. Whereas bacterial utilization of methanol has been reported for many widely different genera and species, the relatively small numbers of methylotrophic yeasts strains identified so far appear to be taxonomically closely related [1]. This kinship is reflected in a remarkable uniformity in the pathways used for methanol metabolism. Although the properties of the various enzymes may slightly differ, all yeasts capable of growth on methanol possess the alcohol oxidase/catalase system for the initial oxidation of the substrate, they oxidise formaldehyde to carbon dioxide via NAD-dependent dehydrogenases and employ the xylulose mono-phosphate (XuMP) pathway for carbon assimilation. A further characteristic that is shared by all species examined is the specific involvement of subcellular organelles and as a result methanol metabolism in yeasts is strictly compartmentalized. This metabolic uniformity is probably also reflected in the mode of regulation of methanol metabolism and although this aspect has been studied in only a limited number of species, the results obtained may be considered representative for the group as a whole.