Deficiency of glucose-6-phosphate dehydrogenase in ace-7 strains of Neurospora crassa

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Both of the two ace-7 strains of Neurospora crassa isolated in this laboratory lack the activity of glucose-6-phosphate dehydrogenase (G6PDH). In starvation culture for acetate, mycelium of ace-7 shows decreased level of NADPH as compared with that of other acetate mutant does. Two NADPH-forming enzymes, malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+) (so called NADP-linked malic enzyme) and isocitrate dehydrogenase (NADP+), are induced by acetate added in culture medium. Acetate seems to make the ace-7 strain grow because it increases the concentration of NADPH by inducing NADPH-forming malic enzyme and isocitrate dehydrogenase. From ace-7 strains, two revertants were obtained which were derived by back mutation on the ace-7 gene and produce qualitatively different G6PDH from the wild type enzyme. This suggests that the ace-7 gene is a structural gene for G6PDH, in addition to the three structural genes proposed by Scott and Tatum (1970).