Identification and characterization of an Ipomoea nil glucosyltransferase which metabolizes some phytohormones

A glucosyltransferase gene InGTase1 was identified from the immature seeds of morning glory (Ipomoea nil), whose product shows a broad substrate-preference, including that of some phytohormones. When 2-trans-abscisic acid, indole-3-acetic acid, salicylic acid (SA) or (±)-jasmonic acid was reacted with InGTase1 and UDP-[14C]-glucose, each 14C-labeled compound with high polarity was detected after thin layer chromatography. SA metabolites were identified as SA glucosyl ester by using 1H NMR and GC/MS. Detailed substrate-preferences of InGTase1 were examined with some analogous compounds, which elucidated that the arm length and/or orientation of a carboxyl group of the compounds or its surrounding electron density severely affected the enzymatic activity. The broad substrate-preference will greatly contribute to the synthesis of various glucoconjugates.