CHARACTERIZATION OF THE INTERACTION OF BETA-CAROTENE-15,15'-DIOXYGENASE FROM RABBIT SMALL-INTESTINE WITH LYCOPENE, 15,15'-DEHYDRO-BETA-CAROTENE, LUTEIN, AND ASTAXANTHINE

Beta-carotene-15,15'-dioxygenase from rabbit small intestine does not form products by cleaving the central double bond of lycopene, 15,15'- dehydro-beta-carotene, lutein, or astaxanthine. Apocarotenals of lutei n and lycopene are formed by non-enzymatic oxidation. Lycopene and 15, 15'-dehydro-beta-carotene competitively inhibit the enzymatic oxidatio n of beta-carotene into retinal. Inhibition of the enzyme by lutein an d astaxanthine is less pronounced, and it is of mired competitive-nonc ompetitive type. Enzymatic formation of retinal from beta-carotene dep ends on the accessibility of substrate molecules.