Many lactic acid bacteria can carry out malolactic fermentation. This secondary fermentation is mediated by the NAD- and Mn2+-dependent malolactic enzyme, which catalyses the decarboxylation of l-malate to l-lactate. The gene we call mleS, coding for malolactic enzyme, was isolated from Lactococcus lactis. The mleS gene consists of one open reading frame capable of coding for a protein with a calculated molecular mass of 59 kDa. The amino acid sequence of the predicted MleS gene product is homologous to the sequences of different malic enzymes. Bacterial and yeast cells expressing the malolactic gene convert l-malate to l-lactate.
