Purification and characterization of glucose-6-phosphate dehydrogenase from Aspergillus niger and Aspergillus nidulans

Abstract

~Glucose-6-phosphate dehydrogenase (G6PD; D-glucose &phosphate:NADP+ oxidoreductase, EC 1.1.1.49) has been purified from AspergiZZus nidulans and AspergiZZus niger by a combination of affinity and anion exchange chromatography. A 500-1000-fold purification was obtained and the final enzyme preparations were shown to be pure but not homogeneous. For both fungi the purified enzyme preparation gave two bands on native and denaturing gels. The catalytically active form is a multimer. The molecular mass of the monomers is 60 and 57 kDa for A. nidulms and 55 and 53 kDa for A , niger. Both enzymes exhibited strict specificity towards both substrates glucose 6-phosphate and NADP+. The A . niduZans and A . niger G6PD enzymes catalyse the conversion of glucose Gphosphate via a random order mechanism. Inhibition studies provided evidence for the physiological role of G6PD as producer of NADPH in both fungi.

Proteome analysis of Aspergillus niger: Lactate added in starch-containing medium can increase production of the mycotoxin fumonisin B2 by modifying acetyl-CoA metabolism

“…Regulation of these enzymes is probably due to an increased NADP:NADPH ratio. The activity of the first enzyme, glucose 6-phosphate dehydrogenase, is known to be regulated by NADP:NADPH levels [50]. Larochelle et al [51] showed in yeast that transcription of the corresponding gene was also affected by the NADPH level and they attributed this to a transcription factor Stb5.…”

Heteroexpression and functional characterization of glucose 6-phosphate dehydrogenase from industrial Aspergillus oryzae

“…According to the specificity of coenzyme, G6PDH can be divided into three categories: NADP [27], A. nidulans [27], A. parasiticus [28] and A. aculeatus [29], also exhibited strict specificity towards NADP + . In all NADP + preferred G6PDHs, the conserved Arg residue was revealed and identified as a determinant in the NADP + specificity [21].…”

On the mechanism of action of the antifungal agent propionate

“…Due to the use of cell‐free extracts, not only the activity of glucose‐6‐phosphate dehydrogenase but also the activity of the 6‐phosphogluconate dehydrogenase was measured. The described method was slightly modified [26]. A typical assay in a final volume of 1 mL contained (in m m ) 50 Mops, pH 7.5; 1 glucose‐6‐phosphate, 1 NADP, 5 EDTA and cell‐free extract.…”