Partial purification and characterization of hydroxycinnamoyl coa transferases from apple and date fruits

Abstract Two hydroxycinnamoyl CoA: transferases (EC 2.3.1.-) (HT) specific for shikimic and quinic acids, which catalyse the formation of 5-O-hydroxycinnamoyl-shikimic and/or -quinic esters, have been purified 82- and 470-fold from young green dates and apples, respectively. They showed highest activity with p-coumaroyl CoA compared with caffeoyl CoA and feruloyl CoA. Both enzymes were active with shikimic and quinic acids, but the relative ratios of the Vmax/Km values for shikimic and quinic acids were found to be 100: 6 for date HT and 23: 100 for apple HT. We, therefore, term the two enzymes hydroxycinnamoyl CoA: shikimate hydroxycinnamoyl transferase (HST) for date and hydroxycinnamoyl CoA: quinate hydroxycinnamoyl transferase (HQT) for apple. The two HTs had similar Mr and optimum pHs and Km values for cinnamoyl-CoA thioesters. The two enzymes exhibited distinct isoelectric point values: 4.63 for HST and 5.40 for HQT.