PURIFICATION AND CHARACTERIZATION OF GLUCOSE-6-PHOSPHATE-DEHYDROGENASE FROM ASPERGILLUS-NIGER AND ASPERGILLUS-NIDULANS

Glucose-6-phosphate dehydrogenase (G6PD; D-glucose 6-phosphate: NADPoxidoreductase, EC 1. 1. 1. 49) has been purified from Aspergillus nid ulans and Aspergillus niger by a combination of affinity and anion exc hange chromatography. A 500-1000-fold purification was obtained and th e final enzyme preparations were shown to be pure but not homogeneous. For both fungi the purified enzyme preparation gave two bands on nati ve and denaturing gels. The catalytically active form is a multimer. T he molecular mass of the monomers is 60 and 57 kDa for A. nidulans and 55 and 53 kDa for A. niger. Both enzymes exhibited strict specificity towards both substrates glucose 6-phosphate and NADP+. The A. nidulan s and A. niger G6PD enzymes catalyse the conversion of glucose 6-phosp hate via a random order mechanism. Inhibition studies provided evidenc e for the physiological role of G6PD as producer of NADPH in both fung i.