NCC malonyltransferase catalyses the final step of chlorophyll breakdown in rape (Brassica napus).

Of the three final products of chlorophyll breakdown that in senescing cotyledons of oilseed rape are accumulated progressively, the nonfluorescent Bn-NCC-1 is the most abundant catabolite. It represents the malonylester of the minor catabolite Bn-NCC-3. The in vitro malonylation of Bn-NCC-3 into Bn-NCC-1 was investigated. Extracts from senescent as well as from presenescent cotyledons contained corresponding activities in the presence of malonyl-coenzyme A as the co-substrate. Malonyltransferase activity exhibited pH- and activation optima at 8 and 34 degrees, respectively, and it was saturable with an apparent Michaelis constant of 58 microM for Bn-NCC-3. The partially purified enzyme recognized chlorophyll catabolites as substrate specifically, provided that they had a free hydroxyl group in the ethyl side chain of pyrrole B.