Comparative Molecular Modeling and Docking Analysis of β-galactosidase Enzymes from Commercially Important Starter Cultures Used in the Dairy Industry

Abstract

β-Galactosidases from S. thermophillus, L. acidophilus, and B. animalis lactis are essential enzymes which hydrolyze lactose during commercial yogurt and cheese production. S. thermophillus β-galactosidase is active in the human digestive tract, improving digestion in lactose-intolerant individuals. Because X-ray crystal structures have not been determined, molecular models of these β-galactosidases were created for comparative structural analysis and molecular docking against lactose. Modeling and docking results were validated using crystal structures of homologous β-galactosidase enzymes from E. coli and B. circulans. The structure of E.coli β-galactosidase in complex with lactose was used as a docking control. Structure-based sequence alignment and molecular docking identified catalytically active residues as GLU458/GLU546 in S. thermophillus, GLU148/GLU307 in L. acidophilus and GLU164/GLU324 in B. animalis ssp. lactis, and predicts residues involved in lactose recognition. These models provide a framework for future engineering of improved β-galactosidase variants with commercial applications.