ENZYMATIC OXIDATION OF BETA-APO-8'-CAROTENOL TO BETA-APO-14'-CAROTENAL BY AN ENZYME DIFFERENT FROM BETA-CAROTENE-15,15'-DIOXYGENASE

Extracts of rat and rabbit intestinal mucosa were fractionated with am monium sulfate. The precipitate contained beta-apocarotenoid-14',13'-d ioxygenase (ADO) activity. beta-Apo-14'-carotenal was found to be the product of enzymatic cleavage of beta-apo-8'-carotenol. Activities of ADO and beta-carotene-15,15'-dioxygenase (CDO) were detected in the pr esence of thiols and were inactivated by 1,10-phenanthroline. Optimal pH values were 7.0 for ADO and 8.0 for CDO. Heating at 52 degrees C in hibited ADO by 70% and produced no effect on CDO. ADO activity was max imal in the presence of sodium cholate or olamidopropyl)-dimethylammon io]-1-propanesulfonate (CHAPS). Sodium dodecylsulfate was required for maximal CDO activity. Proteins with ADO activity were not retained by phenyl-Sepharose CL-4B. CDO activity was eluted from columns only in the presence of detergents. The data suggest that the enzymes that cat alyze the oxidative cleavage of beta-carotene to yield retinal are dif ferent from those that cleave beta-apo-8'-carotenol to yield beta-apo- 14'-carotenal.