Moraxella catarrhalis Lgt2, a galactosyltransferase with broad acceptor substrate specificity

The genetic basis of lipo-oligosaccharide (LOS) biosynthesis for the bacterium Moraxella catarrhalis has been elucidated and functions suggested for each of the glycosyltransferases. In this study we have expressed and characterised one of these enzymes, the putative galactosyltransferase Lgt2_B/C. The lgt2_B/C gene was amplified from M. catarrhalis, expressed in Escherichia coli, and Lgt2_B/C was purified. Analysis of its glycosyltransferase catalytic activity ascertained the pH and temperature optima. The donor specificity and acceptor specificity were examined and they showed that Lgt2_B/C is a galactosyltransferase with relatively broad acceptor specificity with optimal activity in the presence of exogenous Mg²⁺.