Anthocyanin acyltransferase engineered for the synthesis of a novel polyacylated anthocyanin
Some polyacylated anthocyanins, anthocyanins containing two or more aromatic acyl groups, are blue in color within a wide range of pH values, including acidic and neutral conditions even in the absence of any co-pigments or metal ions. We engineered a mutant of a malonyl-CoA:anthocyanin 5-<i>O</i>-glucoside-6″′-<i>O</i>-malonyltransferase of <i>Salvia splendens</i> (Ss5MaT1), Ss5AT306, which has an acquired specificity for hydroxycinnamoyl-CoA and is able to produce novel polyacylated anthocyanins. Ss5AT306 showed 6″′-<i>O</i>-hydroxycinnamoyltransferase activity toward some anthocyanins in addition to the 6″′-<i>O</i>-malonyltransferase activity retained (relative activities for acyl transfer to shisonin: malonyl-CoA, 100%; <i>p</i>-coumaroyl-CoA, 132%; caffeoyl-CoA, 103%). This alteration of acyl-donor specificity was achieved by the substitutions of only three contiguous amino acid residues, Val39-Arg40-Arg41, to the corresponding residues of anthocyanin aromatic acyltransferases, Met-Leu-Gln, suggesting that these amino acid residues are key residues governing the malonyl-CoA specificity of Ss5MaT1. Through the use of Ss5AT306, a novel polyacylated anthocyanin, <i>p</i>-coumaroylshisonin, with one aromatic acyl group in each of the 3-<i>O</i>-glucosyl and 5-<i>O</i>-glucosyl moieties of its structure, was produced and characterized <i>in vitro</i>. <i>p</i>-Coumaroylshisonin was bluer in color and displayed stronger color intensity than did shisonin, implying that accumulation of polyacylated anthocyanins such as <i>p</i>-coumaroylshisonin cause the modulation of flower colors.
- Plant biotechnology
Plant biotechnology 24(5), 495-501, 2007-12-01
Japanese Society for Plant Cell and Molecular Biology