Phosphogluconate dehydrogenase was purified about 20 fold from an adapted strain of Aspergillus niger cultivated on gluconate as the sole carbon source.
The enzyme showed pH optimum between 7.0 to 7.6. The enzyme was activated by glycyl glycine buffer and magnesium ions. Mn ++, Ba++, Ca++ cysteine and reduced glutathione activated the enzyme, while Co++, Zn++, Cu++, Hg++, PCMB and monoiodoacetate inhibit the enzyme.
K~ values for the substmtes, 6-phosphoglueonate and NADP, were found to be 1.66 โข I0 -~ ~ and 8.3 โข 10 -5 ~ respectively.
The purification and properties of phosphogluconate dehydrogenase have been reported from quite a few mieroorgauisms and other biological systems like mammalian liver. One of the earliest reports was that of Hog, exit and SMYR~IOTIS (1951) who purified this enzyme from yeast to about 15 folds. ScoTT and COH~ (1953) isolated the enzyme from Escherichia cell and reported 10 to 12 fold purification. Dw Moss obtained 16.5 fold pure enzyme from Leueonostoc mesenteroides.
The crystallization of phosphoglueonate dehydrogenase was achieved recently by PONTg~MOLI et al. (1961). Phosphogluconate dehydrogenase was also purified from rat liver (GLocK and McLEAn, 1953) and sheep liver (VILL~T and D~zI~L, 1967). Our interest in phosphogluconate dehydrogenase was stimulated by the observations on the adaptive response of the enzyme during cultivation of Aspergillus niger on gluconate as sole carbon source (LAKSHMI~ARAYANA e$ al., 1969b). The present communication describes the partial purification and the characterization of the enzyme from Aslgergiltus niger.
Materials and Methods
The development of the strain, the media and the conditions of cultivation are same as reported previously (I~xs~ARAVA~ et al., 1969a). The following chemicals were used in addition to those which have been reported earlier