[Lactate dehydrogenase and malate dehydrogenase isoenzymes at different stages of the mitotic cycle in Ehrlich tumor cells].

LDH is represented in the tumor almost exclusively by an extremely slow migrating isozyme LDH-5. There is actually no LDH-1, LDH-2, LDH-3 in the spectrum, while LDH-4 is in small amounts. MDH is represented by cytoplasmic isozyme (S-MDH) and a mitochondrial fraction (m-MDH). The activity of LDH-5 and S-MDH is altered in a synchronous way: it shows a very sharp increase at the very beginning of the mitotic cycle and reaches the maximum value already by the mid-S-phase. The m-MDH activity through the cycle is enhanced twice: at the beginning of the cycle and following the termination of S-phase. There was found a direct correlation between the activity of m-MDH and the rate of anaerobic glycolysis through the mitotic cycle of Ehrlich tumor cells.