Benzophenone C-glycosyltransferase involved in the biosynthesis of mangiferin. Exhibits a robust regio- and stereospecific C-glycosylation activity toward over 35 substrates from 18 structurally different types with UDP-glucose. Also able to produce O- and N-glycosides and to use UDP-xylose as sugar donor. Generates only C-glycosides with 2,4,6-tri-hydroxy acceptors at the A ring, both C- and O- glycosides with 2,4-di-hydroxyl acceptors at the A ring, and only O-glycosides with 2- or 4-mono-hydroxy acceptors at the A ring. kcat is 1.6 sec(-1) with maclurin as substrate. kcat is 0.8 sec(-1) with norathyriol as substrate. Optimum pH is 9.0. Optimum temperature is 45 degrees Celsius. Belongs to the UDP-glycosyltransferase family.