Dual 6Pß-Galactosidase/6Pß-Glucosidase GH1 Family for Lactose Metabolism in the Probiotic Bacterium Lactiplantibacillus plantarum WCFS1.

ABSTRACT

Intestinal lactic acid bacteria can help alleviate lactose maldigestion by promoting lactose hydrolysis in the small intestine. This study shows that protein extracts from probiotic bacterium Lactiplantibacillus plantarum WCFS1 possess two metabolic pathways for lactose metabolism, involving ß-galactosidase (ß-gal) and 6Pß-galactosidase (6Pß-gal) activities. As L. plantarum WCFS1 genome lacks a putative 6Pß-gal gene, the 11 GH1 family proteins, in which their 6Pß-glucosidase (6Pß-glc) activity was experimentally demonstrated,, were assayed for 6Pß-gal activity. Among them, only Lp_3525 (Pbg9) also exhibited a high 6Pß-gal activity. The sequence comparison of this dual 6Pß-gal/6Pß-glc GH1 protein to previously described dual GH1 proteins revealed that L. plantarum WCFS1 Lp_3525 belonged to a new group of dual 6Pß-gal/6Pß-glc GH1 proteins, as it possessed conserved residues and structural motifs mainly present in 6Pß-glc GH1 proteins. Finally, Lp_3525 exhibited, under intestinal conditions, an adequate 6Pß-gal activity with possible relevance for lactose maldigestion management.