PURPOSE: To advantageously obtain the subject enzyme useful for production of L-lactic acid by culturing microorganism of genus Streptococcus producing L-lactic acid dehydrogenating enzyme comprising a specific amino acid sequence and collecting said enzyme by separating from the culture material.

CONSTITUTION: A microorganism (e.g. Streptococcus thermophius) belonging to genus Streptococcus producing L-lactic acid dehydrogenating enzyme composed of amino acid sequence expressed by the figure (omitting description of amino acid sequence of from 221th to 327th) is prepared. Next, said microorganism is cultured and produced L-lactic acid dehydrogenating enzyme is separated from the cultured material, then collected to afford the objective L-lactic acid dehydrogenating enzyme composed of amino acid sequence expressed by the figure. By using said enzyme, L-lactic acid can be obtained from pyruvic acid in vitro and L-lactic acid can also be directly produced by culturing a transformed line of lacto bacilli transduced with a gene coding said enzyme.