Zeaxanthin 7,8-dioxygenase

Zeaxanthin 7,8-dioxygenase
Identifiers
EC no.	1.14.99.42
Databases
IntEnz	IntEnz view
BRENDA	BRENDA entry
ExPASy	NiceZyme view
KEGG	KEGG entry
MetaCyc	metabolic pathway
PRIAM	profile
PDB structures	RCSB PDB PDBe PDBsum
Search PMC articles PubMed articles NCBI proteins

Zeaxanthin 7,8-dioxygenase (EC 1.14.99.42, zeaxanthin 7,8(7',8')-cleavage dioxygenase, CsZCD) is an enzyme with systematic name zeaxanthin:oxygen oxidoreductase (7,8-cleaving). ^[1] This enzyme catalyses the following chemical reaction:

zeaxanthin + 2 O₂${\displaystyle \rightleftharpoons }$ crocetin dialdehyde + 2 (3S)-3-hydroxycyclocitral

This enzyme was initially identified in Crocus sativus (saffron), where it was thought to be the key enzyme in the biosynthesis of crocetin, the compound responsible for the characteristic color of saffron spice. It is a member of the carotenoid cleavage dioxygenase (CCD) family of enzymes.

Function and significance

Zeaxanthin 7,8-dioxygenase is a chromoplastic enzyme that catalyzes the oxidative cleavage of zeaxanthin at the 7,8 and 7',8' double bonds. This reaction produces crocetin dialdehyde and 3-hydroxy-β-cyclocitral. Crocetin dialdehyde is a precursor to crocetin and its glycosylated forms, crocins, which are the main pigments in saffron. The other product, 3-hydroxy-β-cyclocitral, is a volatile compound that contributes to the aroma of saffron.

More recent research has suggested that another enzyme, carotenoid cleavage dioxygenase 2 (CCD2), is the primary enzyme responsible for crocetin biosynthesis in saffron, rather than the originally described zeaxanthin 7,8-dioxygenase (often referred to as ZCD or CsZCD). ^[2] This has led to some debate in the scientific literature regarding the precise role and classification of zeaxanthin 7,8-dioxygenase.

The reaction catalyzed by this class of enzymes is of significant commercial interest due to the high value of saffron as a spice and natural food colorant.

References

1. Bouvier F, Suire C, Mutterer J, Camara B (January 2003). "Oxidative remodeling of chromoplast carotenoids: identification of the carotenoid dioxygenase CsCCD and CsZCD genes involved in Crocus secondary metabolite biogenesis". The Plant Cell. 15 (1): 47–62. doi:10.1105/tpc.006536. PMC   143450 . PMID   12509521.
2. Frusciante S, Diretto G, Bruno M, et al. (August 2014). "Novel carotenoid cleavage dioxygenase catalyzes the first dedicated step in saffron crocin biosynthesis". Proc Natl Acad Sci U S A. 111 (33): 12246–12251. Bibcode:2014PNAS..11112246F. doi: 10.1073/pnas.1404629111 . PMC   557688 . PMID   25097262.

External links

• Zeaxanthin+7,8-dioxygenase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)