Mutants of Aspergillus nidulans lacking nicotinamide adenine dinucleotide-specific glutamate dehydrogenase.

Ten mutants of Aspergillus nidulans lacking nicotinamide adenine dinucleotide-specific glutamate dehydrogenase (NAD-GDH) have been isolated, and their mutations (gdhB1 through gdhB10) have been shown to lie in the gdhB gene. In addition, a temperature-sensitive gdhB mutant (gdhB11) has been isolated. A revertant (designated R-5) of the mutant gdhB1 bears an additional lesion in the gdhB gene and has altered NAD-GDH activity with altered Km values for ammonia or ammonium ions and for alpha-ketoglutarate. These results suggest that gdhB specifies a structural component for NAD-GDH. The growth characteristics of gdhB mutants indicate the routes by which amino acids are utilized as nitrogen and carbon energy sources. The properties are described of the double mutants bearing the mutations gdhB1 and gdhA1 or tamA119, which have low NADP-GDH activity.