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
For diagram of reaction click here.
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, CAS registry number:
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. [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. [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. [PMID: 28981773]