Evidence for Two Species of Glutamate Dehydrogenases in Thiobacillus novellus

Abstract

When grown autotrophically in a thiosulfate-mineral salts medium, cells of the facultative chemoautotrophic bacterium, Thiobacillus novellus, produced two distinct glutamate dehydrogenases, one specific for nicotinamide adenine dinucleotide phosphate (NADP) and the other specific for nicotinamide adenine dinucleotide (NAD). When glutamate was supplied exogenously as the sole carbon source, the NAD-specific glutamate dehydrogenase was fully induced. Lower levels of the enzyme were found in bacteria grown in L-arginine, L-alanine, glucose, glycerol, lactate, citrate, or succinate. Arginine, histidine, and aspartate, on the other hand, caused a marked repression of the NADP-specific glutamate dehydrogenase activity. The NAD-dependent glutamate dehydrogenase was allosteric. Adenosine-5'monophosphate and adenosine-5'-diphosphate acted as positive effectors. Both glutamate dehydrogenases were purified about 250-fold and were shown to be distinct protein with different physical properties.

Autotrophic and Heterotrophic Metabolism of Hydrogenomonas: Regulation of Autotrophic Growth by Organic Substrates

“…Of the major nitrogen assimilating catalysts, only glutamate dehydrogenase has been found in H. eutropha (Strenkoski, unpublished data). Its properties are similar to those reported for Thiobacillus novellus (12), and it catalyzes both the synthesis and degradation of glutamate in vitro. Since cells grown on glutamate possess high levels of glutamate dehydrogenase which could presumably function biosynthetically after glutamate exhaustion, the control point for nitrogen assimlation in H. eutropha is probably not the assimilating enzyme itself but may be either the nitrogen uptake mechanism or the synthesis of 2-oxoglutarate.…”

“…The first part involved the formation of 3-phosphoglyceric acid (3-PGA); the second part was the spectrophotometric determination of the amount of 3-PGA formed in part one measured by the oxidation of NADH. The reaction mixture for part one contained 12 jsmoles of MgSO4, 12 ,umoles of reduced glutathione, 80 ,umoles of NaHCO3, 1 ,umole of ribulose diphosphate, 100 ,moles of Tris-hydrochloride buffer (pH 7.9), and the amount of cell extract containing 1.0 mg of protein, in a final volume of 2.0 ml. The mixture was incubated at 37 C for 5 min and then placed in a boiling water bath for 3 min to stop the reaction.…”

Properties of glutamate dehydrogenase from Beta vulgaris

“…These findings are again comparable with data of GDH from other plant sources and bacteria (Bulen 1956, LeJohn and McCrea 1968, Chou and Splittstoesser 1972, Davies and Teixeira 1975, Ehmke and Hartmann 1976. The relation of 2:1 between NADH and NADPH as substrates resembles most closely the dala of Alekhina and Sokolova (1975) for GDH from grain roots.…”

“…This is within the range found in a variety of plants (Pahlich andJoy 1971, Postius 1975). It is in between GDH enzymes of bacterial origin (MW 1.2-2 X H)^ LeJohn and McCrea 1968, LeJohn et al 1969) and those described for animals (MW around 3.5 X 10^ Sund andBurchard 1968, Dessen andPantaloni 1969). The purified enzyme possesses isoenzyme structure, as inferred from gel electrophoresis with subsequent activity staining.…”

Inducible Formation of Glutamate Dehydrogenase in Rice Plant Roots by the Addition of Ammonia to the Media

“…GDH has been shown to exist in both NAD and NADP specific forms in yeast (Doherty 1962), Ncurospora. (Sanwal 1962, Stachow 1967, Strickland 1968, Schizophyllum (Dennen 1967), and Thiobacillus (Lejohn 1968 that deaminating (NAD) and aminating (NADH and NADPH) activities are present in pea roots. NAD, NADH and NADPH activities were also detected in rice plant roots and their properties were investigated.…”