Enzymes: Lactate dehydrogenase and exhausted athletes

When in an oxygenated state, cells are able to generate ATP via oxidative phosphorylation. While this method of ATP production yields a much greater amount of ATP than anaerobic metabolism, it requires oxygen in order to proceed. This means that in some circumstances, anaerobic metabolism will be the preferable path to ATP formation. One example of such a circumstance is during heavy exercise, when the amount of oxygen necessary for oxidative phosphorylation exceeds the amount of usable oxygen being inhaled by the individual. In order to produce the amount of ATP necessary to continue the exercise, the body will switch to anaerobic respiration, which involves repetitive glycolysis and fermentation.

In order to exhaust the high levels of pyruvate that will accumulate from glycolysis, the enzyme Lactate Dehydrogenase metabolizes the pyruvate into lactic acid according to the reaction shown in the figure below. The excess amounts of lactic acid often lead to discomfort or soreness in the areas of the body that underwent the most stress during exercise.

Figure 1. Lactate dehydrogenase converts pyruvate to L-Lactate.