In Vitro Conversion of Carotene to Vitamin A by Chick Liver and Intestine

IT IS generally accepted that the small intestine is a major site for conversion of ingested carotene to vitamin A. Originally, a specific enzyme, carotenase, was assumed to be involved in the process. Recently, however, the hypothesis has been advanced that conversion may take place by β-oxidation of carotene to retinene, followed by reduction of retinene to vitamin A alcohol. With such an hypothesis, a special enzyme, carotenase, would not be required and only normal β-oxidation processes need be postulated. This hypothesis is supported by recent evidence that conversion of carotene to vitamin A can take place in several tissues in addition to the intestine. However, much of the work in this field is inconclusive and contradictory and further information on many aspects of the problem is required. REVIEW OF LITERATURE There is a large volume of literature dealing with problems of conversion of carotene to vitamin A and there …