Purification and characterization of a novel alpha-D-glucosidase from &ITLactobacillus fermentum&IT with unique substrate specificity towards resistant starch

摘要

Resistant starch is not digestible in the small intestine and is fermented by lactic acid bacteria in the large intestine into short chain fatty acids, such as acetate, propionate and butyrate, which result in several health benefits in analogy with dietary fibre components. The mode and mechanism of resistant starch degradation by lactic acid bacteria is still not understood. In the present study, we have purified alpha-D-glucosidase from Lactobacillus fermentum NCDC 156 by employing three sequential steps i.e. ultra filtration, DEAE-cellulose and Sephadex G-100 chromatographies. It was found to be a monomeric protein (similar to 50 kDa). The optimum pH and temperature of this enzyme Were found to be 5.5 and 37 degrees C, respectively. Under optimised conditions with p-nitrophenyl-D-glucopyranoside as the substrate, the enzyme exhibited a K-m of 0.97 mM. Its activity was inhibited by Hg2+ and oxalic acid. N-terminal blocked purified enzyme was subjected to lysyl endopeptidase digestion and the resultant peptides were subjected to BLAST analysis to understand their homology with other alpha-D-glucosidases from lactobacillus species.