STUDIES ON LACTATE DEHYDROGENASE ISOZYMES OF MEGALOBATRACHUS DAVIDIANUS (BLANCHARD)Ⅱ. KINETICS

The optimum pH of LDH1 isozyme of M. davidianus was 7.2 (pyruvate as substrate) and 9.6 (L-lactate as substrate) and LDH5 6.4 (pyruvate as substrate) and 10.0 (L-lactate as substrate). The optimtun temperature of LDH1 was above 37℃ and LDH5 37℃. The thermal stability of LDH1 is higher than that of LDH5. The Km of LDH1 was 2×10-4mol/L (pyruvate as substrate) and 8.5×10-3mol/L (L-lactate as substrate) and LDH5 3×10-4 mol/L (pyruvate as substrate) and 31.2×10-3mol/L (L-lactate as substrate). The LDH1 reached maximum activity at approximately 0.5 mmol/L pyruvate or 50 mmol/L L-ractate, whereas the LDH5 reaches makimum activity at approximately 1.0 mmol/L pyruvate or 300 mmol/L L-lactate.