ID   1.14.99.63
DE   beta-carotene 4-ketolase.
AN   beta-C-4 oxygenase.
AN   beta-carotene ketolase.
CA   (1) 2 AH2 + all-trans-beta-carotene + 2 O2 = 2 A + echinenone + 3 H2O.
CA   (2) 2 AH2 + echinenone + 2 O2 = 2 A + canthaxanthin + 3 H2O.
CC   -!- The enzyme, studied from algae, plants, fungi, and bacteria, adds an
CC       oxo group at position 4 of a carotenoid beta ring.
CC   -!- It is involved in the biosynthesis of carotenoids such as astaxanthin
CC       and flexixanthin.
CC   -!- The enzymes does not act on beta rings that are hydroxylated at
CC       position 3, such as in zeaxanthin (cf. EC 1.14.99.64).
CC   -!- The enzyme from the yeast Xanthophyllomyces dendrorhous is
CC       bifuntional and also catalyzes the activity of EC 1.14.15.24.
DR   Q6J3N5, BKT3_HAELA ;  Q4VKB4, BKT_CHLRE  ;  G3F5K2, BKT_PROBT  ;
DR   Q39982, CRTW_HAELA ;  Q44261, CRTW_PARS1 ;  P54972, CRTW_PARSN ;
//