The Enzyme Database

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EC 1.10.99.3      
Transferred entry: violaxanthin de-epoxidase. Now classified as EC 1.23.5.1, violaxanthin de-epoxidase.
[EC 1.10.99.3 created 2005, deleted 2014]
 
 
EC 1.13.11.51     
Accepted name: 9-cis-epoxycarotenoid dioxygenase
Reaction: (1) a 9-cis-epoxycarotenoid + O2 = 2-cis,4-trans-xanthoxin + a 12′-apo-carotenal
(2) 9-cis-violaxanthin + O2 = 2-cis,4-trans-xanthoxin + (3S,5R,6S)-5,6-epoxy-3-hydroxy-5,6-dihydro-12′-apo-β-caroten-12′-al
(3) 9′-cis-neoxanthin + O2 = 2-cis,4-trans-xanthoxin + (3S,5R,6R)-5,6-dihydroxy-6,7-didehydro-5,6-dihydro-12′-apo-β-caroten-12′-al
For diagram of abscisic-acid biosynthesis, click here
Other name(s): nine-cis-epoxycarotenoid dioxygenase; NCED; AtNCED3; PvNCED1; VP14
Systematic name: 9-cis-epoxycarotenoid 11,12-dioxygenase
Comments: Requires iron(II). Acts on 9-cis-violaxanthin and 9′-cis-neoxanthin but not on the all-trans isomers [2,3]. In vitro, it will cleave 9-cis-zeaxanthin. Catalyses the first step of abscisic-acid biosynthesis from carotenoids in chloroplasts, in response to water stress. The other enzymes involved in the abscisic-acid biosynthesis pathway are EC 1.1.1.288 (xanthoxin dehydrogenase), EC 1.2.3.14 (abscisic-aldehyde oxidase) and EC 1.14.13.93 [(+)-abscisic acid 8′-hydroxylase].
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 199877-10-6
References:
1.  Schwartz, S.H., Tan, B.C., Gage, D.A., Zeevaart, J.A. and McCarty, D.R. Specific oxidative cleavage of carotenoids by VP14 of maize. Science 276 (1997) 1872–1874. [DOI] [PMID: 9188535]
2.  Tan, B.C., Schwartz, S.H., Zeevaart, J.A. and McCarty, D.R. Genetic control of abscisic acid biosynthesis in maize. Proc. Natl. Acad. Sci. USA 94 (1997) 12235–12240. [DOI] [PMID: 9342392]
3.  Qin, X. and Zeevaart, J.A. The 9-cis-epoxycarotenoid cleavage reaction is the key regulatory step of abscisic acid biosynthesis in water-stressed bean. Proc. Natl. Acad. Sci. USA 96 (1999) 15354–15361. [DOI] [PMID: 10611388]
4.  Thompson, A.J., Jackson, A.C., Symonds, R.C., Mulholland, B.J., Dadswell, A.R., Blake, P.S., Burbidge, A. and Taylor, I.B. Ectopic expression of a tomato 9-cis-epoxycarotenoid dioxygenase gene causes over-production of abscisic acid. Plant J. 23 (2000) 363–374. [DOI] [PMID: 10929129]
5.  Iuchi, S., Kobayashi, M., Taji, T., Naramoto, M., Seki, M., Kato, T., Tabata, S., Kakubari, Y., Yamaguchi-Shinozaki, K. and Shinozaki, K. Regulation of drought tolerance by gene manipulation of 9-cis-epoxycarotenoid dioxygenase, a key enzyme in abscisic acid biosynthesis in Arabidopsis. Plant J. 27 (2001) 325–333. [DOI] [PMID: 11532178]
6.  Iuchi, S., Kobayashi, M., Taji, T., Naramoto, M., Seki, M., Kato, T., Tabata, S., Kakubari, Y., Yamaguchi-Shinozaki, K. and Shinozaki, K. Regulation of drought tolerance by gene manipulation of 9-cis-epoxycarotenoid dioxygenase, a key enzyme in abscisic acid biosynthesis in Arabidopsis. Plant J. 30 (2002) 611.
[EC 1.13.11.51 created 2005]
 
 
EC 1.13.11.65     
Accepted name: carotenoid isomerooxygenase
Reaction: zeaxanthin + O2 = (3R)-11-cis-3-hydroxyretinal + (3R)-all-trans-3-hydroxyretinal
For diagram of zeaxanthin biosynthesis, click here
Other name(s): ninaB (gene name)
Systematic name: zeaxanthin:oxygen 15,15′-oxidoreductase (bond-cleaving, cis-isomerizing)
Comments: The enzyme, characterized from the moth Galleria mellonella and the fruit fly Drosophila melanogaster, is involved in the synthesis of retinal from dietary caroteoids in insects. The enzyme accepts different all-trans carotenoids, including β-carotene, α-carotene and lutein, and catalyses the symmetrical cleavage of the carotenoid and the simultaneous isomerization of only one of the products to a cis configuration. When the substrate is hydroxylated only in one side (as in cryptoxanthin), the enzyme preferentially isomerizes the hydroxylated part of the molecule.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Oberhauser, V., Voolstra, O., Bangert, A., von Lintig, J. and Vogt, K. NinaB combines carotenoid oxygenase and retinoid isomerase activity in a single polypeptide. Proc. Natl. Acad. Sci. USA 105 (2008) 19000–19005. [DOI] [PMID: 19020100]
[EC 1.13.11.65 created 2012 as EC 1.14.13.164, transferred 2012 to EC 1.13.11.65]
 
 
EC 1.13.11.84     
Accepted name: crocetin dialdehyde synthase
Reaction: zeaxanthin + 2 O2 = crocetin dialdehyde + 2 3β-hydroxy-β-cyclocitral (overall reaction)
(1a) zeaxanthin + O2 = 3β-hydroxy-8′-apo-β-carotenal + 3β-hydroxy-β-cyclocitral
(1b) 3β-hydroxy-8′-apo-β-carotenal + O2 = crocetin dialdehyde + 3β-hydroxy-β-cyclocitral
Glossary: crocetin dialdehyde = 8,8′-diapocarotene-8,8′-dial
zeaxanthin = (3R,3′R)-β,β-carotene-3,3′-diol
3β-hydroxy-β-cyclocitral = (4R)-4-hydroxy-2,6,6-trimethylcyclohex-1-en-1-carboxaldehyde
Other name(s): CCD2; zeaxanthin 7,8-dioxygenase
Systematic name: zeaxanthin:oxygen 7′,8′-oxidoreductase (bond-cleaving)
Comments: The enzyme, characterized from the plant Crocus sativus (saffron), acts twice, cleaving 3β-hydroxy-β-cyclocitral off each 3-hydroxy end group. It is part of the zeaxanthin degradation pathway in that plant, leading to the different compounds that impart the color, flavor and aroma of the saffron spice. The enzyme can similarly cleave the 7-8 double bond of other carotenoids with a 3-hydroxy-β-carotenoid end group.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Frusciante, S., Diretto, G., Bruno, M., Ferrante, P., Pietrella, M., Prado-Cabrero, A., Rubio-Moraga, A., Beyer, P., Gomez-Gomez, L., Al-Babili, S. and Giuliano, G. Novel carotenoid cleavage dioxygenase catalyzes the first dedicated step in saffron crocin biosynthesis. Proc. Natl. Acad. Sci. USA 111 (2014) 12246–12251. [DOI] [PMID: 25097262]
2.  Ahrazem, O., Rubio-Moraga, A., Berman, J., Capell, T., Christou, P., Zhu, C. and Gomez-Gomez, L. The carotenoid cleavage dioxygenase CCD2 catalysing the synthesis of crocetin in spring crocuses and saffron is a plastidial enzyme. New Phytol. 209 (2016) 650–663. [DOI] [PMID: 26377696]
3.  Ahrazem, O., Diretto, G., Argandona, J., Rubio-Moraga, A., Julve, J.M., Orzaez, D., Granell, A. and Gomez-Gomez, L. Evolutionarily distinct carotenoid cleavage dioxygenases are responsible for crocetin production in Buddleja davidii. J. Exp. Bot. 68 (2017) 4663–4677. [DOI] [PMID: 28981773]
[EC 1.13.11.84 created 2011 as EC 1.14.99.42, modified 2014, transferred 2017 to EC 1.13.11.84]
 
 
EC 1.14.13.90      
Transferred entry: zeaxanthin epoxidase. Now EC 1.14.15.21, zeaxanthin epoxidase
[EC 1.14.13.90 created 2005, deleted 2016]
 
 
EC 1.14.13.129      
Transferred entry: β-carotene 3-hydroxylase. Now EC 1.14.15.24, β-carotene 3-hydroxylase.
[EC 1.14.13.129 created 2011, deleted 2017]
 
 
EC 1.14.13.164      
Transferred entry: carotenoid isomerooxygenase. The enzyme was discovered at the public-review stage to have been misclassified and so was withdrawn. See EC 1.13.11.65, carotenoid isomerooxygenase
[EC 1.14.13.164 created 2012, deleted 2012]
 
 
EC 1.14.15.21     
Accepted name: zeaxanthin epoxidase
Reaction: zeaxanthin + 4 reduced ferredoxin [iron-sulfur] cluster + 4 H+ + 2 O2 = violaxanthin + 4 oxidized ferredoxin [iron-sulfur] cluster + 2 H2O (overall reaction)
(1a) zeaxanthin + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ + O2 = antheraxanthin + 2 oxidized ferredoxin [iron-sulfur] cluster + H2O
(1b) antheraxanthin + 2 reduced ferredoxin [iron-sulfur] cluster + 2 H+ + O2 = violaxanthin + 2 oxidized ferredoxin [iron-sulfur] cluster + H2O
For diagram of the xanthophyll cycle, click here
Other name(s): Zea-epoxidase
Systematic name: zeaxanthin,reduced ferredoxin:oxygen oxidoreductase
Comments: A flavoprotein (FAD) that is active under conditions of low light. Along with EC 1.23.5.1, violaxanthin de-epoxidase, this enzyme forms part of the xanthophyll (or violaxanthin) cycle, which is involved in protecting the plant against damage by excess light. It will also epoxidize lutein in some higher-plant species.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number: 149718-34-3
References:
1.  Buch, K., Stransky, H. and Hager, A. FAD is a further essential cofactor of the NAD(P)H and O2-dependent zeaxanthin-epoxidase. FEBS Lett. 376 (1995) 45–48. [DOI] [PMID: 8521963]
2.  Bugos, R.C., Hieber, A.D. and Yamamoto, H.Y. Xanthophyll cycle enzymes are members of the lipocalin family, the first identified from plants. J. Biol. Chem. 273 (1998) 15321–15324. [DOI] [PMID: 9624110]
3.  Thompson, A.J., Jackson, A.C., Parker, R.A., Morpeth, D.R., Burbidge, A. and Taylor, I.B. Abscisic acid biosynthesis in tomato: regulation of zeaxanthin epoxidase and 9-cis-epoxycarotenoid dioxygenase mRNAs by light/dark cycles, water stress and abscisic acid. Plant Mol. Biol. 42 (2000) 833–845. [PMID: 10890531]
4.  Hieber, A.D., Bugos, R.C. and Yamamoto, H.Y. Plant lipocalins: violaxanthin de-epoxidase and zeaxanthin epoxidase. Biochim. Biophys. Acta 1482 (2000) 84–91. [DOI] [PMID: 11058750]
5.  Frommolt, R., Goss, R. and Wilhelm, C. The de-epoxidase and epoxidase reactions of Mantoniella squamata (Prasinophyceae) exhibit different substrate-specific reaction kinetics compared to spinach. Planta 213 (2001) 446–456. [PMID: 11506368]
6.  Frommolt, R., Goss, R. and Wilhelm, C. Erratum Report. The de-epoxidase and epoxidase reactions of Mantoniella squamata (Prasinophyceae) exhibit different substrate-specific reaction kinetics compared to spinach. Planta 213 (2001) 492.
7.  Matsubara, S., Morosinotto, T., Bassi, R., Christian, A.L., Fischer-Schliebs, E., Luttge, U., Orthen, B., Franco, A.C., Scarano, F.R., Forster, B., Pogson, B.J. and Osmond, C.B. Occurrence of the lutein-epoxide cycle in mistletoes of the Loranthaceae and Viscaceae. Planta 217 (2003) 868–879. [DOI] [PMID: 12844265]
[EC 1.14.15.21 created 2005 as EC 1.14.13.90, transferred 2016 to EC 1.14.15.21]
 
 
EC 1.14.15.24     
Accepted name: β-carotene 3-hydroxylase
Reaction: β-carotene + 4 reduced ferredoxin [iron-sulfur] cluster + 2 H+ + 2 O2 = zeaxanthin + 4 oxidized ferredoxin [iron-sulfur] cluster + 2 H2O (overall reaction)
(1a) β-carotene + 2 reduced ferredoxin [iron-sulfur] cluster + H+ + O2 = β-cryptoxanthin + 2 oxidized ferredoxin [iron-sulfur] cluster + H2O
(1b) β-cryptoxanthin + 2 reduced ferredoxin [iron-sulfur] cluster + H+ + O2 = zeaxanthin + 2 oxidized ferredoxin [iron-sulfur] cluster + H2O
For diagram of lutein biosynthesis, click here and for diagram of zeaxanthin biosynthesis, click here
Other name(s): β-carotene 3,3′-monooxygenase; CrtZ
Systematic name: β-carotene,reduced ferredoxin [iron-sulfur] cluster:oxygen 3-oxidoreductase
Comments: Requires ferredoxin and iron(II). Also acts on other carotenoids with a β-end group. In some species canthaxanthin is the preferred substrate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Sun, Z., Gantt, E. and Cunningham, F.X., Jr. Cloning and functional analysis of the β-carotene hydroxylase of Arabidopsis thaliana. J. Biol. Chem. 271 (1996) 24349–24352. [DOI] [PMID: 8798688]
2.  Fraser, P.D., Miura, Y. and Misawa, N. In vitro characterization of astaxanthin biosynthetic enzymes. J. Biol. Chem. 272 (1997) 6128–6135. [DOI] [PMID: 9045623]
3.  Fraser, P.D., Shimada, H. and Misawa, N. Enzymic confirmation of reactions involved in routes to astaxanthin formation, elucidated using a direct substrate in vitro assay. Eur. J. Biochem. 252 (1998) 229–236. [DOI] [PMID: 9523693]
4.  Bouvier, F., Keller, Y., d'Harlingue, A. and Camara, B. Xanthophyll biosynthesis: molecular and functional characterization of carotenoid hydroxylases from pepper fruits (Capsicum annuum L.). Biochim. Biophys. Acta 1391 (1998) 320–328. [DOI] [PMID: 9555077]
5.  Linden, H. Carotenoid hydroxylase from Haematococcus pluvialis: cDNA sequence, regulation and functional complementation. Biochim. Biophys. Acta 1446 (1999) 203–212. [DOI] [PMID: 10524195]
6.  Zhu, C., Yamamura, S., Nishihara, M., Koiwa, H. and Sandmann, G. cDNAs for the synthesis of cyclic carotenoids in petals of Gentiana lutea and their regulation during flower development. Biochim. Biophys. Acta 1625 (2003) 305–308. [DOI] [PMID: 12591618]
7.  Choi, S.K., Matsuda, S., Hoshino, T., Peng, X. and Misawa, N. Characterization of bacterial β-carotene 3,3′-hydroxylases, CrtZ, and P450 in astaxanthin biosynthetic pathway and adonirubin production by gene combination in Escherichia coli. Appl. Microbiol. Biotechnol. 72 (2006) 1238–1246. [DOI] [PMID: 16614859]
[EC 1.14.15.24 created 2011 as EC 1.14.13.129, transferred 2017 to EC 1.14.15.24]
 
 
EC 1.14.99.42      
Transferred entry: zeaxanthin 7,8-dioxygenase. Now EC 1.13.11.84, crocetin dialdehyde synthase
[EC 1.14.99.42 created 2011, modified 2014, deleted 2017]
 
 
EC 1.14.99.63     
Accepted name: β-carotene 4-ketolase
Reaction: (1) β-carotene + 2 reduced acceptor + 2 O2 = echinenone + 2 acceptor + 3 H2O
(2) echinenone + 2 reduced acceptor + 2 O2 = canthaxanthin + 2 acceptor + 3 H2O
For diagram of canthaxanthin biosynthesis, click here
Glossary: echinenone = β,β-caroten-4-one
canthaxanthin = β,β-carotene-4,4′-dione
zeaxanthin = β,β-carotene-3,3′-diol
astaxanthin = 3,3′-dihydroxy-β,β-carotene-4,4′-dione
Other name(s): BKT (ambiguous); β-C-4 oxygenase; β-carotene ketolase; crtS (gene name); crtW (gene name)
Systematic name: β-carotene,donor:oxygen oxidoreductase (echinenone-forming)
Comments: The enzyme, studied from algae, plants, fungi, and bacteria, adds an oxo group at position 4 of a carotenoid β ring. It is involved in the biosynthesis of carotenoids such as astaxanthin and flexixanthin. The enzyme does not act on β rings that are hydroxylated at position 3, such as in zeaxanthin (cf. EC 1.14.99.64, zeaxanthin 4-ketolase). The enzyme from the yeast Xanthophyllomyces dendrorhous is bifuntional and also catalyses the activity of EC 1.14.15.24, β-carotene 3-hydroxylase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Lotan, T. and Hirschberg, J. Cloning and expression in Escherichia coli of the gene encoding β-C-4-oxygenase, that converts β-carotene to the ketocarotenoid canthaxanthin in Haematococcus pluvialis. FEBS Lett. 364 (1995) 125–128. [PMID: 7750556]
2.  Breitenbach, J., Misawa, N., Kajiwara, S. and Sandmann, G. Expression in Escherichia coli and properties of the carotene ketolase from Haematococcus pluvialis. FEMS Microbiol. Lett. 140 (1996) 241–246. [PMID: 8764486]
3.  Steiger, S. and Sandmann, G. Cloning of two carotenoid ketolase genes from Nostoc punctiforme for the heterologous production of canthaxanthin and astaxanthin. Biotechnol. Lett. 26 (2004) 813–817. [PMID: 15269553]
4.  Ojima, K., Breitenbach, J., Visser, H., Setoguchi, Y., Tabata, K., Hoshino, T., van den Berg, J. and Sandmann, G. Cloning of the astaxanthin synthase gene from Xanthophyllomyces dendrorhous (Phaffia rhodozyma) and its assignment as a β-carotene 3-hydroxylase/4-ketolase. Mol. Genet. Genomics 275 (2006) 148–158. [PMID: 16416328]
5.  Tao, L., Yao, H., Kasai, H., Misawa, N. and Cheng, Q. A carotenoid synthesis gene cluster from Algoriphagus sp. KK10202C with a novel fusion-type lycopene β-cyclase gene. Mol. Genet. Genomics 276 (2006) 79–86. [PMID: 16625353]
6.  Kathiresan, S., Chandrashekar, A., Ravishankar, G.A. and Sarada, R. Regulation of astaxanthin and its intermediates through cloning and genetic transformation of β-carotene ketolase in Haematococcus pluvialis. J. Biotechnol. 196-197 (2015) 33–41. [PMID: 25612872]
[EC 1.14.99.63 created 2018]
 
 
EC 1.14.99.64     
Accepted name: zeaxanthin 4-ketolase
Reaction: (1) zeaxanthin + 2 reduced acceptor + 2 O2 = adonixanthin + 2 acceptor + 3 H2O
(2) adonixanthin + 2 reduced acceptor + 2 O2 = (3S,3′S)-astaxanthin + 2 acceptor + 3 H2O
Glossary: zeaxanthin = β,β-carotene-3,3′-diol
adonixanthin = 3,3′-dihydroxy-β,β-carotene-4-one
(3S,3′S)-astaxanthin = (3S,3′S)-3,3′-dihydroxy-β,β-carotene-4,4′-dione
Other name(s): BKT (ambiguous); crtW148 (gene name)
Systematic name: zeaxanthin,donor:oxygen oxidoreductase (adonixanthin-forming)
Comments: The enzyme has a similar activity to that of EC 1.14.99.63, β-carotene 4-ketolase, but unlike that enzyme is able to also act on zeaxanthin.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Zhong, Y.J., Huang, J.C., Liu, J., Li, Y., Jiang, Y., Xu, Z.F., Sandmann, G. and Chen, F. Functional characterization of various algal carotenoid ketolases reveals that ketolating zeaxanthin efficiently is essential for high production of astaxanthin in transgenic Arabidopsis. J. Exp. Bot. 62 (2011) 3659–3669. [PMID: 21398427]
2.  Huang, J., Zhong, Y., Sandmann, G., Liu, J. and Chen, F. Cloning and selection of carotenoid ketolase genes for the engineering of high-yield astaxanthin in plants. Planta 236 (2012) 691–699. [PMID: 22526507]
[EC 1.14.99.64 created 2018]
 
 
EC 1.23.5.1     
Accepted name: violaxanthin de-epoxidase
Reaction: violaxanthin + 2 L-ascorbate = zeaxanthin + 2 L-dehydroascorbate + 2 H2O (overall reaction)
(1a) violaxanthin + L-ascorbate = antheraxanthin + L-dehydroascorbate + H2O
(1b) antheraxanthin + L-ascorbate = zeaxanthin + L-dehydroascorbate + H2O
For diagram of the xanthophyll cycle, click here
Glossary: violaxanthin = (3S,3′S,5R,5′R,6S,6′S)-5,6:5′,6′-diepoxy-5,5′,6,6′-tetrahydro-β,β-carotene-3,3′-diol
antheraxanthin = (3R,3′S,5′R,6′S)-5′,6′-epoxy-5′,6′-dihydro-β,β-carotene-3,3′-diol
zeaxanthin = (3R,3′R)-β,β-carotene-3,3′-diol
Other name(s): VDE
Systematic name: violaxanthin:ascorbate oxidoreductase
Comments: Along with EC 1.14.15.21, zeaxanthin epoxidase, this enzyme forms part of the xanthophyll (or violaxanthin) cycle for controlling the concentration of zeaxanthin in chloroplasts. It is activated by a low pH of the thylakoid lumen (produced by high light intensity). Zeaxanthin induces the dissipation of excitation energy in the chlorophyll of the light-harvesting protein complex of photosystem II. In higher plants the enzyme reacts with all-trans-diepoxides, such as violaxanthin, and all-trans-monoepoxides, but in the alga Mantoniella squamata, only the diepoxides are good substrates.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 57534-73-3
References:
1.  Yamamoto, H.Y. and Higashi, R.M. Violaxanthin de-epoxidase. Lipid composition and substrate specificity. Arch. Biochem. Biophys. 190 (1978) 514–522. [DOI] [PMID: 102251]
2.  Rockholm, D.C. and Yamamoto, H.Y. Violaxanthin de-epoxidase. Plant Physiol. 110 (1996) 697–703. [PMID: 8742341]
3.  Bugos, R.C., Hieber, A.D. and Yamamoto, H.Y. Xanthophyll cycle enzymes are members of the lipocalin family, the first identified from plants. J. Biol. Chem. 273 (1998) 15321–15324. [DOI] [PMID: 9624110]
4.  Kuwabara, T., Hasegawa, M., Kawano, M. and Takaichi, S. Characterization of violaxanthin de-epoxidase purified in the presence of Tween 20: effects of dithiothreitol and pepstatin A. Plant Cell Physiol. 40 (1999) 1119–1126. [PMID: 10635115]
5.  Latowski, D., Kruk, J., Burda, K., Skrzynecka-Jaskierm, M., Kostecka-Gugala, A. and Strzalka, K. Kinetics of violaxanthin de-epoxidation by violaxanthin de-epoxidase, a xanthophyll cycle enzyme, is regulated by membrane fluidity in model lipid bilayers. Eur. J. Biochem. 269 (2002) 4656–4665. [DOI] [PMID: 12230579]
6.  Goss, R. Substrate specificity of the violaxanthin de-epoxidase of the primitive green alga Mantoniella squamata (Prasinophyceae). Planta 217 (2003) 801–812. [DOI] [PMID: 12748855]
7.  Latowski, D., Akerlund, H.E. and Strzalka, K. Violaxanthin de-epoxidase, the xanthophyll cycle enzyme, requires lipid inverted hexagonal structures for its activity. Biochemistry 43 (2004) 4417–4420. [DOI] [PMID: 15078086]
[EC 1.23.5.1 created 2005 as EC 1.10.99.3, transferred 2015 to EC 1.23.5.1]
 
 
EC 2.4.1.276     
Accepted name: zeaxanthin glucosyltransferase
Reaction: 2 UDP-glucose + zeaxanthin = 2 UDP + zeaxanthin bis(β-D-glucoside)
For diagram of zeaxanthin biosynthesis, click here
Other name(s): crtX (gene name)
Systematic name: UDP-glucose:zeaxanthin β-D-glucosyltransferase
Comments: The reaction proceeds in two steps with the monoglucoside as an intermediate.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Hundle, B.S., O'Brien, D.A., Alberti, M., Beyer, P. and Hearst, J.E. Functional expression of zeaxanthin glucosyltransferase from Erwinia herbicola and a proposed uridine diphosphate binding site. Proc. Natl. Acad. Sci. USA 89 (1992) 9321–9325. [DOI] [PMID: 1409639]
[EC 2.4.1.276 created 2011]
 
 
EC 5.3.3.22     
Accepted name: lutein isomerase
Reaction: lutein = meso-zeaxanthin
For diagram of lutein biosynthesis, click here
Glossary: lutein = (3R,3′R)-dihydroxy-α-carotene
meso-zeaxanthin = (3R,3′S)-β,β-carotene-3,3′-diol
Other name(s): RPE65 (gene name); meso-zeaxanthin isomerase
Systematic name: lutein Δ4-Δ5-isomerase
Comments: The enzyme is found in the retinal pigment epithelium (RPE) of vertebrates. It also has the activity of EC 3.1.1.64, retinoid isomerohydrolase.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Shyam, R., Gorusupudi, A., Nelson, K., Horvath, M.P. and Bernstein, P.S. RPE65 has an additional function as the lutein to meso-zeaxanthin isomerase in the vertebrate eye. Proc. Natl. Acad. Sci. USA 114 (2017) 10882–10887. [DOI] [PMID: 28874556]
[EC 5.3.3.22 created 2018]
 
 


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