STUDY OF COMPLEX-FORMATION BETWEEN NAD KINASE AND GLUTAMATE-DEHYDROGENASE FROM RABBIT LIVER HYALOPLASM

Evidence for the localization of up to 25-30% of the total glutamate d ehydrogenase (GluDH) activity in rabbit liver cell hyaloplasm has been obtained Differences were revealed in the properties of GluDH from th e hyaloplasm and mitochondria. The ratios of activities in the aminati on/deamination reactions measured at optimal pH values for the mitocho ndrial and hyaloplasmic enzymes were 3.7 and 1.0, respectively. The en zyme preparations isolated from both fractions appeared to be electrop horetically homogeneous and had subunit molecular weight (MW) of about 56 +/- 2 kD. Fresh preparations of mitochondrial and hyaloplasm liver GluDH contained several oligomeric forms, predominantly with MW of 35 0 and 280 kD respectively Data from gel filtration on Sephacryl S-300 are suggestive of complex (MW = 800 kD) formation between liver hyalop lasm GluDH (280 kD) and NAD kinase (440 kD), this being accompanied by simultaneous activation of the enzymes (3.5- and 2.4-fold, respective ly).