2 FLAVONOID-SPECIFIC MALONYLTRANSFERASES FROM CELL-SUSPENSION CULTURES OF PETROSELINUM-HORTENSE - PARTIAL-PURIFICATION AND SOME PROPERTIES OF MALONYL-COENZYME A - FLAVONE-FLAVONOL-7-O-GLYCOSIDE MALONYLTRANSFERASE AND MALONYL-COENZYME A - FLAVONOL-3-O-GLUCOSIDE MALONYLTRANSFERASE

Two malonyltransferases were isolated from irradiated cell suspension cultures of parsley (P. hortense) and extensively purified. One enzyme was most active with flavone and flavonol-7-O-glycosides as substrates; the other enzyme preferentially malonylated flavonol-3-O-glucosides. The substrate specificity of the enzymes in vitro was in agreement with the pattern of malonylated flavonoid glycosides occurring in the cell cultures in vivo. The apparent Km values for the most efficient substrates, including the donor of the acyl residue, malonyl-CoA, were .apprx. 4-20 .mu.M. Both malonyltransferases had an apparent MW of .apprx. 50,000.