Glycerol Metabolism in Yeasts: Pathways of Utilization and Production

Abstract

The utilization of glycerol by Candida utilis has been studied. It has been found that this yeast has a permeability for glycerol and other three carbon compounds much greater than that of baker's yeast. This permeability allows the entrance of glycerol in Candida cells rapidly enough to permit its efficient utilization even at low concentrations. The inducibility of glycerol kinase has been established. An increase in the concentration of the mitochondrial L-α-glycerophosphate oxidase when the yeast is grown on glycerol has also been observed. A model is presented for the substrate specificity pattern of glycerol kinase of C. mycoderma. It postulates the involvement of three hydroxyl groups in the spatial distribution corresponding to the formation of L-α-glycerophosphate from glycerol. This requirement can be met by aldo-and ketotrioses in their respective hydrated forms. The pathway of glycerol formation in S. cerevisiae has also been studied. Evidence is shown of the existence of a NADH dependent enzymatic activity reducing triose phosphate to α-glycerophosphate which can roughly account for the glycerol production. A low ionic strength seems to be required for the activity of this enzyme. The α-glycerophosphatase is specific for the L from, the efficiency of α-glycerophosphatase on D-α-glycerophosphate being 1/30 of that on L-α-glycerophosphate. The concentration of the α-glycerophosphatase in yeasts is higher when grown on hexoses than when grown on non-sugar carbon sources.