Polyol dehydrogenases from silkworm eggs: Purification and properties

Abstract

Extract from silkworm eggs contains two kinds of nicotinamide adenine dinucleotide phosphate (NADP)-specific polyol dehydrogenases, which catalyse the dehydrogenation of various polyols as well as the reduction of a number of sugars to the corresponding polyol. These are designated as polyol dehydrogenase-I and -II. The purified polyol dehydrogenase-I catalyses the reduction of glucose, xylose, erythrose and d,l-glyceraldehyde but does not catalyse the reduction of the phosphate esters of sugars (except ribose-5-phosphate, R-5-p). Polyol dehydrogenase-II catalyses the reduction of glucose-6-phosphate (G-6-P) as well as xylose, erythrose and d,l-glyceraldehyde, but does not catalyse the reduction of hexoses (except galactose). The molecular weights of polyol dehydrogenase-I and -II were determined to be 56,000 and 76,000 respectively by gel filtration.The roles of these dehydrogenases are discussed in relation to the metabolic pathway which leads to the accumulation of sorbitol and glycerol in the diapausing silkworm eggs.