Regulation of Staphylococcus aureus Lactate Dehydrogenase

The effect of growth conditions on the specific activity of nicotinamide adenine dinucleotide (NAD)-linked lactate dehydrogenase (LDH) in extracts of Staphylococcus aureus strain SG 511A was examined. Kinetic and electrophoretic experiments, with extracts prepared from aerobically and anaerobically grown cells, provided evidence for only one physiologically significant enzyme. The aerobic level of NAD-linked LDH of S. aureus remained constant and was independent of the carbon source. In contrast, the level of LDH produced in an anaerobic environment was variable and was dependent on the carbon source. Growth anaerobically on pyruvate, as the sole fermentable carbon source, resulted in a maximal level of LDH activity, a value about eightfold greater than the aerobic level. Anaerobic growth either on pyruvate plus glucose or on glucose alone, however, resulted in approximately a threefold decrease in this maximum. Experiments with a heme-requiring auxotroph derived from S. aureus demonstrated that the aerobic level of LDH activity was dependent on a functional respiratory chain.