The Interrelation between Transketolase and Dihydroxyacetone Synthase Activities in the Methylotrophic Yeast Candida boidinii

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Abstract
Crude extracts of C. boidinii grown on glucose, xylose or ethanol gave single peaks of classical transketolase activity following chromatography on columns of hydroxylapatite; the enzyme was heat-stable and showed no appreciable activity with formaldehyde as acceptor in place of ribose 5-phosphate. Extracts of methanol-grown cells showed 2 peaks of transketolase activity following chromatography on both hydroxylapatite and DEAE-cellulose. One peak was identified with that found for the cells grown on substrates other than methanol; the other peak showed dihydroxyacetone synthase activity in addition to transketolase activity. Both activities in the latter peak were very unstable and were ascribed to 1 enzyme on the basis of identical rates of denaturation at all temperatures tested between 0-40.degree. C. This enzyme may be a special transketolase synthesized only during methylotrophic growth of the yeast and, in contrast to classical transketolase, may be capable of using equally well either formaldehyde or ribose 5-phosphate as glycolaldehyde acceptor. A method based on heat treatment was suggested for the simultaneous assay of both transketolases present in crude extracts of a methylotrophically grown yeast.

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