[Study of complex formation between NAD-kinase and glutamate dehydrogenase, isolated from rabbit liver hyaloplasm]

Evidence for the localization of up to 25-30% of the total glutamate dehydrogenase activity in rabbit liver cell hyaloplasm has been obtained. Differences were revealed in the properties of glutamate dehydrogenase from the hyaloplasm and mitochondria. The ratios of activities in the amination/deamination reactions as measured at optimal values of pH for the mitochondrial and liver enzymes were 3.7 and 1.0, respectively. The enzyme preparations isolated from the both fractions appeared to be electrophoretically homogeneous and had a subunit molecular mass of about 56 +/- 2 kDa. Fresh preparations of mitochondrial and hyaloplasm liver glutamate dehydrogenase contained several oligomeric forms, predominantly with M of 350 and 280 kDa, respectively. Data from gel-filtration on Sephacryl S-300 are suggestive of a complex (M = 800 kDa) formation between liver hyaloplasm glutamate dehydrogenase (280 kDa) and NAD-kinase (440 kDa); this reaction is accompanied by simultaneous activation of these enzymes (3.5- and 2.4-fold, respectively).