Cloned (Comment) | Organism |
---|---|
gene crtO, phylogenetic tree, recombinant expression in Escherichia coli | Synechocystis sp. |
Organism | UniProt | Comment | Textmining |
---|---|---|---|
Synechocystis sp. | Q55808 | gene crtO | - |
Purification (Comment) | Organism |
---|---|
recombinant enzyme from Escherichia coli | Synechocystis sp. |
Reaction | Comment | Organism | Reaction ID |
---|---|---|---|
beta-carotene + benzoquinone + H2O = echinenone + benzoquinol + 2 H+ | proposed mechanism for the formation of the 4-keto group at the beta-ionone ring, overview | Synechocystis sp. |
Substrates | Comment Substrates | Organism | Products | Comment (Products) | Rev. | Reac. |
---|---|---|---|---|---|---|
4,4'-dihydroxy-beta-carotene + benzoquinone | via 4-hydroxy-4'-oxo-beta-carotene | Synechocystis sp. | canthaxanthin + benzoquinol | - |
? | |
beta-carotene + benzoquinone + H2O | - |
Synechocystis sp. | echinenone + benzoquinol + 2 H+ | - |
? | |
additional information | CrtO substrate specificity, the enzyme is basically a mono ketolase, only small amounts of diketo canthaxanthin are formed due to the low relative turnover numbers for the mono ketoechinenone, overview. Also other carotenoids with an unsubstituted beta-ionone ring are utilized with low conversion rates by CrtO regardless of the substitutions at the other end of the molecule. The CrtO ketolase is independent of oxygen and utilizes an oxidized quinone as co-factor. The first catalytic step involved hydride transfer to the quinone. The stabilization reaction of the resulting carbo cation is a reaction with OH- forming a hydroxy group, the keto group results from two subsequent hydroxylations at the same C-atom and water elimination | Synechocystis sp. | ? | - |
? |
Synonyms | Comment | Organism |
---|---|---|
carotenoid ketolase | - |
Synechocystis sp. |
CrtO | - |
Synechocystis sp. |
CrtO ketolase | - |
Synechocystis sp. |
Temperature Optimum [°C] | Temperature Optimum Maximum [°C] | Comment | Organism |
---|---|---|---|
28 | - |
assay at | Synechocystis sp. |
pH Optimum Minimum | pH Optimum Maximum | Comment | Organism |
---|---|---|---|
7.8 | - |
assay at | Synechocystis sp. |
Cofactor | Comment | Organism | Structure |
---|---|---|---|
quinone | - |
Synechocystis sp. |
General Information | Comment | Organism |
---|---|---|
evolution | CrtO belongs to the CrtI family which comprises carotene desaturases and carotenoid oxidases. Phylogenetic tree of beta-carotene 4-ketolase CrtO and other enzymes related to bacterial phytoene desaturases CrtI including CrtN (4,4'-diapophytoene desaturase), CrtNb (4,4'-diapolycopene oxidase) and CrtNc (4,4'-diapolycopene-4,40-dial oxidase), overview | Synechocystis sp. |
metabolism | CrtW and CrtO are two distinct non-homologous beta-carotene ketolases catalyzing the formation of echinenone and canthaxanthin | Synechocystis sp. |
additional information | the CrtO reaction is fundamentally different to the CrtW ketolase reaction, EC 1.14.11.B16, which ketolates the same substrate to the same product in an oxygen-dependent dioxygenase reaction | Synechocystis sp. |