Characterization and engineering of glycosyltransferases responsible for steroid saponin biosynthesis in Solanaceous plants

SaGT4A from Solanum aculeatissimum glucosylates both steroidal sapogenins and steroidal alkaloids. StSGT from S. tuberosum prefers UDP-galactose to UDP-glucose as a sugar donor. In vitro mutagenesis and chimeric enzymatic studies were performed for these glycosyltransferases.