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)-3,5-dihydroxy-6,7-didehydro-5,6-dihydro-12'-apo-β-caroten-12'-al
For diagram 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. [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. [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. [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. [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. [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. Erratum. Plant J. 30 (2002) 611. [PMID: 11532178]