A Study of Derepression of NAD-specific Glutamate Dehydrogenase of Neurospora crassa

Abstract

Transfer of Neurospora crassa mycelium from a 1% (w/v) sucrose medium to carbon-free or 1% (w/v) glutamate medium results in the onset of derepression of the catabolic NAD-specific glutamate dehydrogenase (NAD-GDH), within 30 min of the shift. Immunoprecipitation of in vivo pulse-labelled NAD-GDH demonstrated that this enzyme was synthesized de novo, correlating with increasing enzyme activity in shifted cells. Derepression was shown to be under transcriptional control by using the RNA synthesis inhibitor, picolinic acid, and by immunoprecipitation of the in vitro translation products of poly(A)-containing mRNA from repressed and derepressed cells. A brief (5 min) shift to derepression medium followed by a return to 1% (w/v) sucrose medium was sufficient to trigger synthesis of abundant NAD-GDH transcripts and low levels of the active enzyme. A secondary level of translational control is proposed to account for the discrepancy between the detectable levels of NAD-GDH transcripts and protein, following transient derepression.

The gdhB Gene of Pseudomonas aeruginosa Encodes an Arginine-Inducible NAD + -Dependent Glutamate Dehydrogenase Which Is Subject to Allosteric Regulation

“…AERUGINOSA CATABOLIC GLUTAMATE DEHYDROGENASE 497 from P. aeruginosa, described here, the amino acid sequence of the enzyme from B. subtilis was reported to be very similar to many other hexameric glutamate dehydrogenases from different bacterial species (4). In contrast, the tetrameric NADGDHs from Neurospora crassa and yeasts, which are presumed to function specifically in glutamate catabolism, are indeed induced by glutamate (21,40), as well as by carbon or nitrogen starvation (33,45). However, it would be interesting to know whether these eukaryotic NAD-GDHs are also inducible by arginine.…”

The NADP-Dependent Glutamate Dehydrogenase of Giardia lamblia: A Study of Function, Gene Structure and Expression

“…Class II GDHs are tetrameric proteins which are NAD-dependent and are involved in the conversion of glutamate to a-ketoglutarate for catabolic purposes. The distribution of the class II GDHs are limited to some unicellular eukaryotes such as the yeasts, Saccharomyces cerevisiae, and Neurospora crassa (Vierula and Kapoor, 1989;Miller and Magasanik, 1990). All organisms characterized to date which have a class II GDH also have a class I GDH.…”

NAD+-dependent glutamate dehydrogenase of the edible mushroom Agaricus bisporus: biochemical and molecular characterization

“…In contrast to the wealth of biochemical, biophysical and amino acid sequence data available for the hexameric GDHs, the tetrameric NAD + -dependent enzymes are less well understood. In ascomycetes the NAD-GDH is derepressed during growth on glutamate or by carbon starvation, and repressed by ammonium (Goldin and Frieden 1971;Vierula and Kapoor 1989;Coschigano et al 1991;Miller and Magasanik 1991). In basidiomycetes the data are less conclusive (Dennen and Niederpruem 1964;Stewart and Moore 1974;Chalot et al 1991;Schwartz et al 1991;Baars et al 1995b).…”