[Properties of lactate dehydrogenase of brain mitochondria].

The activity of lactate dehydrogenase in the brain mitochondria isolated within the phycol density gradient accounts for 5% of the enzyme activity determined in cytoplasm. More than 80% of this activity is found in the intermembrane space of mitochondria. Purification, washing and incubation of the mitochondria with supernatant fluid do not change the activity. The treatment with lubrol, desoxycholate or ultrasound evoked almost a two-fold increase in the enzymic activity in the mitochondria and does not change it in the supernatant fluid. Rotenone and Ca2+ have no effect on the activity of lactate dehydrogenase in the both preparations, KCN inhibits it. Mg2+ increases the activity in the supernatant fluid and decreases it in the mitochondria. The relative amount of M- and N- forms of lactate dehydrogenase is approximately the same in the both studied objects.