Enzymatic preparation of 1-O-hydroxycinnamoyl-β-D-glucoses as acyl donors to acylate anthocyanin, and substrate preference of 1-O-hydroxycinnamoyl-β-D-glucose-dependent acyltransferase in anthocyanin-synthesizing cultured Daucus carota and Glehnia littoralis cells

Abstract

Preparing 1-O-hydroxycinnamoyl-β-D-glucoses (HCA-Glc) as an acyl donor is prerequisite to studying HCA-Glc-dependent acyltransferase to anthocyanins. Four HCA-Glcs (sinapoyl-, feruloyl-, caffeoyl-, and 4-coumaroyl-glucose) were synthesized using a recombinant protein for Gomphrena globosa sinapate glucosyltransferase coupled with a UDP-glucose recycling system using Arabidopsis thaliana sucrose synthase. The substrate preference for HCA-Glc-dependent acyltransferase activity was examined in a protein extract prepared from anthocyanin-synthesizing cultured cells of Daucus carota and Glehnia littoralis. The sinapoyl moiety in D. carota and the feruloyl-moiety in G. littoralis were modified to be identical to the anthocyanin molecule of in vivo aglycone and sugar moieties. The protein extracts from both D. carota and G. littoralis cultured cells showed higher activity for feruloyl-Glc than for sinapoyl-Glc. These results suggested that these species have different specificity for acyl donor molecules in vivo rather than indicating a substrate preference of acyltransferase enzymes in vitro.