[Effect of inorganic anions on the activity of dental pulp lactate dehydrogenase]

Pig dental pulp lactate dehydrogenase (EC. 1.1.1.27; LDH) isozymes were separated by DEAE Sephadex A-50 column chromatography, and LDH-1 isozyme was purified by blue dextran affinity chromatography. The specific activity of pig dental pulp LDH-1 was 193.2 units/mg protein, and the purified enzyme showed a single protein band on disk electrophoresis. In this paper, we studied the effect of inorganic ions on the activity of pig dental pulp LDH-1 isozyme, and compared it with that of affected by anions. Dental pulp and heart muscle LDH-1 isozymes were inhibited at a low pyruvate concentration; otherwise, at a high pyruvate concentration, each enzyme activity was enhanced by the anions. But the effect of SO2(2-) was different from that of the other anions: SO2(2-) did not activate the enzyme at a high pyruvate concentration. In the dental pulp, the Km values for pyruvate were 1 order of magnitude smaller by SO2(2-), and 1 order higher by other anions than the control value. In the heart muscle, the Km values were not changed by anions, except by SO2(2-).