Physicochemical and Regulatory Properties of Lactate Dehydrogenase from Pea (Pisum sativum L.) Leaves under Oxygen Deficiency

Resumo

Lactate dehydrogenase activity (LDH, EC 1.1.1.27) was induced in pea (Pisum sativum L.) leaves by culturing plants under flood conditions. The enzyme was purified to an electrophoretic homogeneous state with a multistage purification process including ammonium sulfate fractionation, ion exchange chromatography on DEAE-sephacel, and gel chromatography on Sephadex G-200. The LDH preparation had a specific activity of 41.9 E/mg protein, with a purification rate of 101 and a yield of 26.8%. Its physical and chemical features were studied. The molecular weight of the native LDH molecule (148 kD) was determined, and the enzyme was shown to consist of four subunits, the molecular mass of which was determined by PAGE-Na electrophoresis in the presence of SDS-Na equal to 37 kD. The kinetic and regulatory properties, such as the Michaelis constants, the substrate inhibition constants, the effects of hydrogen-ion and temperature on the direct and reverse reactions, were studied.