Purification and characterization of lactate dehydrogenase from Varanus liver

Abstract

Lactate dehydrogenase was purified 21-fold from liver of Varanus bengalensis using colchicine-sepharose column chromatography. The crude enzyme showed two isoenzymes (LDH-5 and LDH-4) by agarose gel electrophoresis (AGE). The purified enzyme showed a single band after SDS-PAGE corresponding to molecular mass of 35 kDa. The molecular mass of native enzyme was about 140 kDa. The optimum pH for the forward reaction was 7.5 while that for the reverse reaction was pH 9.5. The K(m) values for pyruvate, NADH, lactate and NAD+ were 0.17 ± 0.037, 0.02 ± 0.004, 12.4 ± 3.05 and 0.38 ± 0.032 mM, respectively. Pre-heating of enzyme showed that its t50 was 40-50°C. Oxalate and n-hexanediol were inhibitors for both forward and reverse reactions. Among divalent ions, Cu++ was shown to be more effective inhibitor for the forward reaction.