Eat Your Carrots!

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Science  12 May 2000:
Vol. 288, Issue 5468, pp. 931
DOI: 10.1126/science.288.5468.931b

Although β-carotene is known to be the 40-carbon precursor for the 20-carbon retinoids and thus for retinol (vitamin A), purification and identification of the vitamin A-generating enzyme has been elusive until now. By relying on sequence homology to a plant carotene-cleaving dioxygenase (which produces the growth regulator abscisic acid), von Lintig and Vogt identified a Drosophila gene encoding a 70-kilodalton protein that converted β-carotene to retinal. This gene maps to the same location as the Drosophila mutant ninaB, which displays a reduced content of rhodopsin, the protein that uses a covalently linked retinal chromophore to detect photons. The enzyme appears to utilize Fe in the oxidative cleavage of the double bond, and characterization of its mammalian counterpart is anticipated.—GJC

J. Biol. Chem.275, 11915 (2000).

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