G6PD in immature and mature human brain. Electrophoretic and enzyme kinetic studies.

The isoenzyme polymorphism and kinetics of glucose-6-phosphate dehydrogenase (G6PD) in embryonal and mature brain were studied. Two types of electropherograms were found in embryonal brains: type I is characterized by two G6PD fractions: slow and fast, and in the type II a single, fast-moving G6PD fraction was seen in a single embryo. The additional studies carried out, namely reelectrophoresis following 2-mercaptoethanol and NADP treatment and the specific enzyme kinetics, i.e. altered Michaelis constant and enhanced utilization of the desamino-NADP analogue which are typical of the fast-moving fraction in embryonal brain, speak unequivocally in favor of the presence of a new, unknown, phase-specific isoenzyme of G6PD. Its synthesis takes place only during embryonal brain development. A probable autosomal localization for the gene of brain G6PD is suggested.