Malonyl-coenzyme A:isoflavone 7-O-glucoside-6"-O-malonyltransferase from roots of chick pea (Cicer arietinum L.)

A malonyltransferase which catalyzes the malonylation of isoflavone 7-O-glucosides in position 6 of the glucose moiety using malonyl-coenzyme A as acyl donor has been purified 157-fold from 4-day-old roots of chick pea (Cicer arietinum L.). The enzyme showed a pH optimum of 8.0 and a molecular weight of 112,000. The Km for malonylcoenzyme A was 48 microM and, for the chick pea isoflavones biochanin A and formononetin, 36 and 24 microM, respectively. Various other isoflavone, flavone, and flavonol 7-O-glucosides and chalcone 4'-O-glucosides were much poorer substrates. Flavonol 3-O-glucosides and isoflavone 4'-O-glucosides were not malonylated by the malonyltransferase.