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

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Abstract
The MW, the amino acid composition and the N[amino]-terminal and C[carboxyl]-terminal amino acids of 2 allosteric (L. casei, L. curvatus) and 2 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 substrate-binding site of the L-lactate dehydrogenase of several animals. The essential cysteine residue 165 is replaced by threonine as in the L-lactate dehydrogenase of lobster. The 4 bacterial peptides differ by 2 changes in single amino acid residues from each and from those of animals. The data indicate that not only the animal L-lactate dehydrogenases, but also the allosteric and the non-allosteric lactate dehydrogenases from bacterial sources probably evolved from a common gene.