[On intratetrametric catalytic independency of active sites of lactate dehydrogenase isoenzymes].

Interrelations of active sites of tetrameric molecules of human lactatedehydrogenase (LDH), known as intratetrameric catalytic independency of subunits, are studied. Estimation of catalytic activity of subunits, which compose hybrid LDH isoenzymes, is carried out. Ratios of molecular activity of subunits are calculated and a conclution is drawn on the catalytic independency of LDH isoenzymes active sites with respect to substrate inhibition by L-lactate. Possible mechanisms of substrate inhibition of LDH isoenzymes and their inactivation with urea in the view of different interrelations of active sites of these isoenzymes under conditions studied are discussed.