Expression, Purification and Kinetic Characterization of Lactate Dehydrogenase of Lactic Acid Bacteria and ProB of Bacillus subtilis

Abstract

Lactate dehydrogenase is very well known for its role in glucose metabolism in Lactic Acid Bacteria (LAB). These bacteria are widely used in the industrial and research areas. LAB use NADH as a cofactor to produce lactate or lactic acid from glucose through fermentation, whereas ProB is an enzymatic protein which catalyzes the conversion of L-glutamate to ?-glutamyl phosphate at the expense of ATP in proline biosynthesis. Both the recombinant proteins are expressed in the E. coli BL 21 strain using pET plasmids. Proteins are purified using affinity chromatography and purity is established by a single band in SDS Page. Proteins were quantified by Bradford assay. In this study, the proteins selected are Lactate Dehydrogenase and ProB. In the absence of FBP, Pi is an activator of L. lactis LDH at pH 6. This effect can be interpreted by considering the computed binding affinities of Pi to the catalytic and allosteric binding sites of the enzymes modelled in protonation states corresponding to pH 6 and pH 7. In this study, we can find out the delicate interplay among the effects of Pi, FBP, and pH that results in different regulatory effects on the LDH of LAB and ProB of B. subtilis.