Abstract: The enzyme D-2-hydroxy-4-methylpentanoic acid dehydrogenase has been prepared by culturing readily available Lactobacillus or Leuconostoc, microorganisms, such as Lactobacillus casei ssp. pseudoplantarum and Leuconostoc mesenteroides. The microbiologically produced enzyme has special characteristics and is capable of converting D-2-hydroxycarboxylic acids, such as D-2-hydroxy-4-methylpentanoic acid to the corresponding 2-ketocarboxylic acid and is capable of enzymatically converting 2-ketocarboxylic acids, such as 2-keto-4-methylpentanoic acid and 2-ketobutyric acid to the corresponding D-2-hydroxycarboxylic acid.