Demonstration and Solubilization of Lycopene Cyclase from Capsicum Chromoplast Membranes

Abstract

The conversion of phytoene into fl-carotene was demonstrated previ-ously in chromoplast membranes prepared from Capsicum fruits (B. Camara et al. 1982 Eur J Biochem 127: 255-258). The direct cyclization of lycopene into fl-carotene and the successful solubilization of the enzymic activity involved in this reaction is reported. incubation time, the reaction was stopped by the addition of 4 ml of chloroform:methanol (2:1, v/v). Carrier amounts (100 ,g) of i-carotene, y-carotene, a-carotene, and lycopene were added to facilitate the location of the reaction products. Preliminary chromatography was achieved on Silica Gel G plates developed with 40 to 60°C petroleum ether ether (99:1, v/v), which sepa-rates the bicyclic carotene fraction (a-carotene and ,Bcarotene with a higher RF value) from lycopene (lower RF value). The Through the use of isolated chromoplast membranes, we have shown that labeled phytoene is desaturated, isomerized, and cyclized to yield ,B-carotene (6). Lycopene plays a mandatory role in this sequence of reactions in that it is the direct substrate for cyclization, as shown by Camara and Moneger (7). We report here the direct cyclization oflycopene by Capsicum chromoplast membranes and the solubilization of the enzymic activity