Background: Lactate dehydrogenases (LDHs) are key metabolic enzymes in lactic acid bacteria (LAB). Results: The effects of fructose 1,6-bisphosphate, phosphate, pH, and ionic strength on enzyme activity differ for six LDHs from four LAB. Conclusion: The regulation of LDH activity differs among LAB. Significance: These results have implications for understanding enzyme evolutionary adaptation, for quantitative comparative modeling, and for biotechnological application of LAB. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc.