The Enzymatic Cleavage of B-Carotene: End of a Controversy

  • This review was prepared by George Wolf, D.Phil., Department of Nutritional Sciences and Toxicology, University of California, Berkeley, CA 94720-3104, USA, and is dedicated to the memory of Dr. James A. Olson. Please address all reprint requests to the Nutrition Reviews Editorial Office, 711 Washington Street, Boston, MA 02111, USA.


The central cleavage of dietary B-carotene to retinal was found to be the predominant mechanism whereby retinoids were formed in vivo in rats; apocarotenals, indicative of eccentric cleavage of B-carotene, were only a minor component (<5% of retinoids). A gene from maize that codes for a plant carotenoid cleavage enzyme was used to isolate a homologous gene from Drosophila. This gene, when transfected into an E Coli strain capable of synthesizing and accumulating B-carotene, caused the central cleavage of B-carotene, forming exclusively retinoids. The enzyme that the gene codes for, B-carotene-15,15'-dioxygenase, was purified and characterized.