The human enzyme that converts dietary provitamin A carotenoids to vitamin A is a dioxygenase.
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dela Sena C, Riedl KM, Narayanasamy S, Curley RW Jr, Schwartz SJ, Harrison EH
The human enzyme that converts dietary provitamin A carotenoids to vitamin A is a dioxygenase.
J Biol Chem. 2014 May 9;289(19):13661-6. doi: 10.1074/jbc.M114.557710. Epub 2014 Mar 25.
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- 24668807 [ View in PubMed]
- Abstract
beta-Carotene 15-15'-oxygenase (BCO1) catalyzes the oxidative cleavage of dietary provitamin A carotenoids to retinal (vitamin A aldehyde). Aldehydes readily exchange their carbonyl oxygen with water, making oxygen labeling experiments challenging. BCO1 has been thought to be a monooxygenase, incorporating oxygen from O2 and H2O into its cleavage products. This was based on a study that used conditions that favored oxygen exchange with water. We incubated purified recombinant human BCO1 and beta-carotene in either (16)O2-H2(18)O or (18)O2-H2(16)O medium for 15 min at 37 degrees C, and the relative amounts of (18)O-retinal and (16)O-retinal were measured by liquid chromatography-tandem mass spectrometry. At least 79% of the retinal produced by the reaction has the same oxygen isotope as the O2 gas used. Together with the data from (18)O-retinal-H2(16)O and (16)O-retinal-H2(18)O incubations to account for nonenzymatic oxygen exchange, our results show that BCO1 incorporates only oxygen from O2 into retinal. Thus, BCO1 is a dioxygenase.