Information on EC - beta-carotene 4-ketolase

for references in articles please use BRENDA:EC1.14.99.63
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IUBMB Comments
The enzyme, studied from algae, plants, fungi, and bacteria, adds an oxo group at position 4 of a carotenoid beta ring. It is involved in the biosynthesis of carotenoids such as astaxanthin and flexixanthin. The enzyme does not act on beta rings that are hydroxylated at position 3, such as in zeaxanthin (cf. EC, zeaxanthin 4-ketolase). The enzyme from the yeast Xanthophyllomyces dendrorhous is bifuntional and also catalyses the activity of EC, beta-carotene 3-hydroxylase.
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The expected taxonomic range for this enzyme is: Bacteria, Eukaryota
alr3189, beta-C-4 oxygenase;, beta-C-4-oxygenase, beta-carotene 3-hydroxylase/4-ketolase, beta-carotene 4,4'-oxygenase, beta-carotene ketolase, bkt, bkt1, BKT3, CrtO, more
beta-carotene + 2 reduced acceptor + 2 O2 = echinenone + 2 acceptor + 3 H2O
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echinenone + 2 reduced acceptor + 2 O2 = canthaxanthin + 2 acceptor + 3 H2O
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