Anthocyanin galactosyltransferase from Aralia cordata, cDNA cloning and characterization

Abstract

The UDF-galactose: anthocyanin 3-O-galactosyltransferase (ACGaT) cDNA was cloned from cell-suspension cultures of Aralia cordata Thunb. (Araliaceae). The cDNA was isolated from a cDNA library using a galactosyltransferase cDNA from Vigna mungo. The cDNA contained an open reading frame encoding 452 amino acids with a calculated molecular mass of 50.0 kDa. The deduced amino acid sequence of ACGaT cDNA included a plant secondary product glycosyltransferase signature sequence and was similar to the flavonoid 3-O-glycosyltransferases from petunia and grape. The enzymatic activity of the recombinant ACGaT expressed in Escherichia coli was detected toward anthocyanins and flavonols as an aglycon and UDP-galactose as a sugar donor. The reaction product for quercetin and UDP-galactose catalyzed by the recombinant ACGaT was identified as quercetin 3-O-β-galactoside using nuclear magnetic resonance spectroscopy.