Substrate Specificity of the Galactokinase from the Human Gut Symbiont Akkermansia Muciniphila ATCC BAA-835

Galactokinases, which catalyze the phosphorylation of galactose and possible other monosaccharides, can provide an activated sugar donor to synthesize sugar-containing molecules. In this study, a novel galactokinase from human gut symbiont Akkermansia muciniphila ATCC BAA-835 (GalKAmu) was expressed and characterized. GalKAmu displayed broad substrate tolerance, with catalytic activity towards Gal (100 %), GalN (100 %), GalA (20.2 %), Glc (52.5 %), GlcNAc (15.5 %), Xyl (<5%), ManNAc (58 %), ManF (37.4 %) and l-Glc (80 %). Most interestingly, this was the first GalK isoform which can tolerate ManNAc. Thus, our characterization of GalKAmu broadens the substrate selection of galactokinases.