Functional Characterization of Residues Affecting the Catalytic Activity of Glucosyltransferase from <i>Streptococcus mutans</i>

Dental caries is a multifactorial, biofilm-mediated disease primarily caused by <i>Streptococcus mutans</i>, a key etiological agent. This bacterium secretes extracellular enzymes known as glucosyltransferases (Gtfs), also termed glucansucrases, which play a pivotal role in the synthesis of exopolysaccharides through the metabolism of dietary sucrose. These exopolysaccharides provide binding sites for the attachment and colonization of other microorganisms, contributing to the initiation and progression of dental caries. This study investigates the catalytic mechanisms of glucosyltransferases from <i>S. mutans</i> using molecular dynamics simulations, with a focus on the conformational dynamics and interactions of amino acid residues that modulate enzymatic activity. Wild-type and mutant models of glucosyltransferase, bound to maltose, sucrose (substrates), and acarbose (an inhibitor), were generated to analyze the binding patterns of these molecules. The systems' stability was assessed using root-mean-square deviation, fluctuation, radius of gyration, principal component analysis, free energy landscape, and dynamic cross-correlation matrix analysis. The MMGBSA method was employed to evaluate the relative binding free energies of the systems. Our findings revealed that mutations increased stability in the sucrose-bound system while decreasing stability in the acarbose-bound system, with consistent fluctuation patterns observed across different ligands. These dynamic changes in glucosyltransferase behavior could influence its catalytic efficiency.