Comparative studies of lactate dehydrogenases in lactic acid bacteria. Amino-acid composition of an active-site region and chemical properties of the L-lactate dehydrogenase of Lactobacillus casei, Lactobacillus curvatus, Lactobacillus plantarum, and Lactobacillus acidophilus.

The molecular weight, the amino acid composition and the N-terminal and C-terminal amino acids of two allosteric (Lactobacillus casei, L. curvatus) and two non-allosteric (L. plantarum, L. acidophilus) L-lactate dehydrogenases, purified to homogeneity by affinity chromatography, were determined. The amino acid composition of the only tryptic peptide unequivocally common to the fingerprints of the 4 enzymes is virtually identical with that of the arginine peptide, called Arg6 of the the substratebinding site of the L-lactate dehydrogenase dehydrogenase of several animals. However, the 'essential' cysteine residue 165 is replaced by threonine, as it is in the L-lactate dehydrogenase of lobster. In addition, the 4 bacterial peptides differ by one or two changes in single amino acid residues from each other as well as from those of animals. The data indicate that not only the animal L-lactate dehydrogenases, but also the allosteric and lactate dehydrogenases from bacterial sources may have evolved from a common gene.