Regulation of Glutamate Dehydrogenases During Morphogenesis of Schizophyllum commune

Abstract

The specific activities of two glutamate dehydrogenases (GDH), one requiring nicotinamide adenine dinucleotide (NAD) and the other specific for nicotinamide adenine dinucleotide phosphate (NADP), varied during growth of Schizophyllum commune as a function of the stage of the life cycle and the exogenous nitrogen source. During basidiospore germination on either glucose-NHa or glucose-glutamate medium, NADP-GDH increased six-to eightfold in specific activity, whereas NAD-GDH was depressed. During dikaryotic mycelial growth on either nitrogen source, the two GDH increased in a 1:1 ratio, whereas, during homokaryotic mycelial growth on glucose-NH3, NADP-GDH activity was depressed and NAD-GDH increased six-to eightfold. Homokaryotic mycelium cultured on glucose-glutamate medium yielded high NADP-GDH activities and normal NAD-GDH activities. Intracellular NH3 concentration and NADP-GDH activities were inversely related during spore germination and homokaryotic mycelium growth, whereas guanosine-5'-triphosphate (GTP) and L-glutamine specifically inhibited NAD-and NADP-GDH respectively in vitro. GTP inhibition was shown in extracts from cells at all stages of the life cycle. Basidiospore germling extracts contained an NADP-GDH essentially resistant to L-glutamine inhibition.

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.…”

Cytodifferentiation and morphogenesis in Schizophyllum commune.

“…Homokaryotic mycelium cultured on glutamate medium shows parallel increases in both GDH activities of S. commune, in contrast to a depressed NAD-specific GDH seen during glutamate germination. Dikaryotic mycelium of S. commune cultured on glucose-ammonia shows ratios of near unity for NAD-and NADPcoupled GDH (19). The observation of parallel GDH activities also rules out the possibility that reciprocal regulation occurs throughout development.…”

“…Changes in specific activities of two glutamate dehydrogenases of S. commune during basidiospore germination on culture medium containing either (NH4)%SO4 or L-glutamate as sole nitrogen source. After Dennen and Niederpruem (19 (19). This drug also causes total cessation of the development of NADP-GDH in conidia of N. crassa (100).…”

“…Moreover, ammonia represses the NAD-specific GDH in yeast (7,8,29,67,118), which is also contrary to that of mycelium of S. commune. Since these comparative biochemical studies revealed basic differences in the regulation of GDH in N. crassa, yeast, and S. commune, control of GDH activities was studied during basidiospore germination, mycelial growth, and dikaryotization of S. commune (19).…”

“…However, the rate of glutamate oxidation in vivo during differentiation of the slime mold Dictyoslelium discoideum is thought to be governed by endogenous substrates (14,124). The physiological basis for the depressed NAD-GDH in basidiospore germination of S. commune is not known, although the lack of ammonia regulation of the NADP-GDH could be explained by low amounts of intracellular ammonia at this stage (19).…”