Molecular and Structural Characterization of a Promiscuous C-Glycosyltransferase from Trollius chinensis
Herein, the catalytic promiscuity of TcCGT1, a new C-glycosyltransferase (CGT) from the medicinal plant Trollius chinensis is explored. TcCGT1 could efficiently and regio-specifically catalyze the 8-C-glycosylation of 36 flavones and other flavonoids and could also catalyze the O-glycosylation of diverse phenolics. The crystal structure of TcCGT1 in complex with uridine diphosphate was determined at 1.85 ? resolution. Molecular docking revealed a new model for the catalytic mechanism of TcCGT1, which is initiated by the spontaneous deprotonation of the substrate. The spacious binding pocket explains the substrate promiscuity, and the binding pose of the substrate determines C- or O-glycosylation activity. Site-directed mutagenesis at two residues (I94E and G284K) switched C- to O-glycosylation. TcCGT1 is the first plant CGT with a crystal structure and the first flavone 8-C-glycosyltransferase described. This provides a basis for designing efficient glycosylation biocatalysts.
Exploring the catalytic promiscuity of a new glycosyltransferase from Carthamus tinctorius
The catalytic promiscuity of a new glycosyltransferase (UGT73AE1) from Carthamus tinctorius was explored. UGT73AE1 showed the capability to glucosylate a total of 19 structurally diverse types of acceptors and to generate O-, S-, and N-glycosides, making it the first reported trifunctional plant glycosyltransferase. The catalytic reversibility and regioselectivity were observed and modeled in a one-pot reaction transferring a glucose moiety from icariin to emodin. These findings demonstrate the potential versatility of UGT73AE1 in the glycosylation of bioactive natural products.
A TRIFOLIRHIZIN MALONATE FROM SOPHORA FLAVESCENS VAR. ANGUSTIFOLIA AND ITS STABILITY
Trifolirhizin 6''-O-malonate was isolated both from the roots and callus cultures of Sophora flavescens var. angustifolia and identified by HPLC, MS and NMR.