L-serine enhances the anaerobic lactate metabolism of Veillonella dispar ATCC 17745.

Abstract

Under anaerobic conditions, the rate of metabolism of lactate by starved resting cells of Veillonella dispar ATCC 17745 was very low. Because pyruvate was metabolized well by the starved cells, oxidation of lactate to pyruvate, which is the first step of the lactate metabolism, must have been limited in the cells. In the starved cells, the levels of the metabolic intermediates, oxalacetate or fumarate, of which reductions to malate or to succinate could be coupled with lactate oxidation to pyruvate and initiate lactate metabolism, were quite low, suggesting that these had been reduced during the starvation steps under strictly anaerobic conditions. Thus, the starved cells were unable to start the anaerobic lactate metabolism because of shortage of such reducible substrates. L-serine greatly enhanced anaerobic lactate metabolism of the starved cells. This enhancement may have been due to metabolism of L-serine itself and conversion to oxalacetate and fumarate, which made it possible to begin lactate oxidation.