Malolactic enzyme of Lactobacillus plantarum. Purification, properties, and distribution among bacteria.

The malolactic enzyme of Lactobacillus plantarum was purified from 5.5 units/mg to a specific activity of 265 units/mg of protein. The enzyme has an isoelectric point of pH 4.4. The molecular weight is Mr = 140,000 as determined by gradient gel electrophoresis. The enzyme consists of two probably identical subunits (Mr = 70,000) that were observed after treatment with sodium dodecyl sulfate. Malolactic enzyme catalyzes the NAD- and manganese-dependent reaction L-malate leads to CO2 + L-lactate. Therefore, this enzyme can be distinguished from the well known malic enzymes (L-malate: NAD+ oxidoreductase, oxalacetate-decarboxylating EC 1.1.1.38 or 1.1.1.39). Malolactic enzyme is found in most lactic acid bacteria (Lactobacteriaceae); it has not been detected in other bacteria.