A PHYLOGENIC STUDY OF ANIMAL GLUCOSE 6-PHOSPHATE DEHYDROGENASES

Abstract

The glucose 6-phosphate dehydrogenases from a variety of animals and from yeast were compared using such parameters as the substrate specificity, effects of nicotinamide adenine dinucleotide phosphate on the electrophoretic mobility, solubility in ammonium sulfate, chromatographic behavior on DEAE-Sephadex columns.Although the animal glucose 6-phosphate dehydrogenases exist in a variety of molecular forms, they were classified for convenience into three major types, I, II and III, based on the substrate specificity; Type I enzymes are active on glucose 6-phosphate only, Type II enzymes are active on glucose 6-phosphate and galactose 6-phosphate, and Type III enzymes are also active on deoxyglucose 6-phosphate. Type I was further divided into two subtypes, A and B, based on the effect of nicotinamide adenine dinucleotide phosphate on the electrophoretic mobility of enzymes.It has been found that Type I-A is the most common form among animals, and is the only form in yeast and paramecium, that Type II is present in invertebrates and in lower vertebrates, while Type III occurs exclusively in vertebrates. The results indicated the possibility that Type II and Type III might have evolved from Type I G6PD.