Chlorophyll breakdown in ripening fruits of Capsicum annuum

Colour changes from green to red taking place during ripening of Capsicum annztum fruits are due to transition from chloroplast to chromopIast in the exocarp. It was investigated whether the pathway of chlorophyll breakdown in developing chromoplasts comprises the same enzymatic steps as in the chloroplasts of senescent leaves. Chromoplast membranes contained high activities of phaeophorbide a oxygenase, a key enzyme of chlorophyll breakdown, which in senescent leaves has previously been identified to be responsible for the oxygenolytic cleavage of the porphyrin macrocycle. properties such as specificity for Pheide a as substrate, requirement for reduced ferredoxin as well as lack of activity in the absence of stroma protein were identical to those of the enzyme from senescent leaves. The first identifiable product of Pheide a cleavage, a colourless fluorescent catabolite, was slightly less polar than the corresponding FCC produced by the oxygenase from barley or rape leaves.