Regio- and Stereospecific O-Glycosylation of Phenolic Compounds Catalyzed by a Fungal Glycosyltransferase from Mucor hiemalis

Glycosylated small molecules are often bioactive and obtained mainly via microbial biotransformation especially by fungi. However, no responsible glycosylation gene/enzyme has yet been uncovered in a filamentous fungus. We report here the first identification of a phenolic glycosyltransferase MhGT1 from Mucor hiemalis. The substrate promiscuity of the new phenolic O-glycosyltransferase was explored by using phenols from Traditional Chinese Medicinal herbs as substrates. MhGT1 exhibited robust capabilities for the regio- and stereospecific O-glycosylation of 72 structurally diverse drug-like scaffolds and sterols with uridine diphosphate (UDP) glucose as a sugar donor. Unprecedentedly, MhGT1 showed higher regiospecificities and activities for prenylated phenols than for their non-prenylated analogues. Computational modelling of MhGT1 uncovered a truncated N-terminal domain of the enzyme consisting of hydrophobic and charged amino acid residues which contributed to the broad substrate scope and regiospecificity towards prenylated compounds. Our findings expand the ways to obtain new glycosyltransferases and also effectively apply the enzymatic approach to obtain glycosylated compounds in drug discovery.