An enzymatic alteration secondary to adenylyl cyclase deficiency in the cr-1 (crisp) mutant of Neurospora crassa: Nicotinamide adenine dinucleotide (phosphate) glycohydrolase overproduction

Abstract

The vegetative growth of the adenylyl cyclase-deficient mutant cr-1 (crisp), of Neurospora crassa, resembled a conidiogenic microcycle. It was demonstrated that an enzyme which is exclusively confined to conidia in wild-type strains, i.e., nicotinamide adenine dinucleotide (phosphate) glycohydrolase (NAD(P)ase; EC 3.2.2.6), was continuously released in the culture medium by the mutant. NAD(P)ase activity of agitated cr-1 cultures was much lower than that of standing cultures; nevertheless, the enzyme was actively produced immediately after agitation was stopped. Supplementation of the growth medium with cyclic AMP normalized the morphological phenotype of the cr-1 mutant and drastically reduced NAD(P)ase production. These results suggest that NAD(P)ase regulation is somehow dependent on cyclic AMP metabolism. However, the effect of the nucleotide over the enzyme does not appear to be direct, since other crisp mutants, cr-2 and cr-3, which also overproduced NAD(P)ase, were completely unresponsive to cyclic AMP. These strains possess normal adenylyl cyclase activity.