:Chlorophyllide-a oxygenase

{{Short description|Class of enzymes}}

{{Infobox enzyme

| Name = Chlorophyllide-a oxygenase

| EC_number = 1.14.13.122

| CAS_number = 216503-73-0

| GO_code =

| image =

| width =

| caption =

}}

Chlorophyllide-a oxygenase ({{EC number|1.14.13.122}}), chlorophyllide a oxygenase, chlorophyll-b synthase, CAO) is an enzyme with systematic name chlorophyllide-a:oxygen 7-oxidoreductase.{{cite journal | vauthors = Espineda CE, Linford AS, Devine D, Brusslan JA | title = The AtCAO gene, encoding chlorophyll a oxygenase, is required for chlorophyll b synthesis in Arabidopsis thaliana | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 96 | issue = 18 | pages = 10507–11 | date = August 1999 | pmid = 10468639 | pmc = 17919 | doi = 10.1073/pnas.96.18.10507 | bibcode = 1999PNAS...9610507E | doi-access = free }}{{cite journal | vauthors = Oster U, Tanaka R, Tanaka A, Rüdiger W | title = Cloning and functional expression of the gene encoding the key enzyme for chlorophyll b biosynthesis (CAO) from Arabidopsis thaliana | journal = The Plant Journal | volume = 21 | issue = 3 | pages = 305–10 | date = February 2000 | pmid = 10758481 | doi = 10.1046/j.1365-313x.2000.00672.x | doi-access = free }}{{cite journal | vauthors = Eggink LL, LoBrutto R, Brune DC, Brusslan J, Yamasato A, Tanaka A, Hoober JK | title = Synthesis of chlorophyll b: localization of chlorophyllide a oxygenase and discovery of a stable radical in the catalytic subunit | journal = BMC Plant Biology | volume = 4 | pages = 5 | date = April 2004 | pmid = 15086960 | pmc = 406501 | doi = 10.1186/1471-2229-4-5 | doi-access = free }}{{cite journal | vauthors = Porra RJ, Schäfer W, Cmiel E, Katheder I, Scheer H | title = The derivation of the formyl-group oxygen of chlorophyll b in higher plants from molecular oxygen. Achievement of high enrichment of the 7-formyl-group oxygen from 18O2 in greening maize leaves | journal = European Journal of Biochemistry | volume = 219 | issue = 1–2 | pages = 671–9 | date = January 1994 | pmid = 8307032 | doi = 10.1111/j.1432-1033.1994.tb19983.x | url = https://epub.ub.uni-muenchen.de/2482/1/244.pdf | doi-access = free }} This enzyme catalyses the following chemical reactions

: (1) chlorophyllide a + O₂ + NADPH + H⁺ $\backslash rightleftharpoons$ 7-hydroxychlorophyllide a + H₂O + NADP⁺

: (2) 7-hydroxychlorophyllide a + O₂ + NADPH + H⁺ $\backslash rightleftharpoons$ chlorophyllide b + 2 H₂O + NADP⁺

File:C-3 position Chlorophyll a.svg show in the green box is oxidised to a formyl group.]]

This enzyme contains a mononuclear iron centre and is part of the biosynthetic pathway to chlorophylls.{{cite journal |title=Biosynthesis of chlorophylls from protoporphyrin IX |last =Willows | first =Robert D. | journal =Natural Product Reports | year =2003 | volume = 20 |issue = 6 | pages =327–341 |doi=10.1039/B110549N |pmid=12828371}}{{cite journal |doi=10.1007/s11120-006-9076-6 |title=Recent advances in chlorophyll biosynthesis |year=2007 |last1=Bollivar |first1=David W. |journal=Photosynthesis Research |volume=90 |issue=2 |pages=173–194 |pmid=17370354 |s2cid=23808539 }}