Any feedback?
Please rate this page
(literature.php)
(0/150)

BRENDA support

Literature summary for 1.17.5.B2 extracted from

  • Breitenbach, J.; Gerjets, T.; Sandmann, G.
    Catalytic properties and reaction mechanism of the CrtO carotenoid ketolase from the cyanobacterium Synechocystis sp. PCC 6803 (2013), Arch. Biochem. Biophys., 529, 86-91.
    View publication on PubMed
Search for more literature for 1.17.5.B2

Cloned(Commentary)

Cloned (Comment) Organism
gene crtO, phylogenetic tree, recombinant expression in Escherichia coli Synechocystis sp.

Organism

Organism UniProt Comment Textmining
Synechocystis sp. Q55808 gene crtO
-

Purification (Commentary)

Purification (Comment) Organism
recombinant enzyme from Escherichia coli Synechocystis sp.

Reaction

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.
a

Substrates and Products (Substrate)

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

Synonyms Comment Organism
carotenoid ketolase
-
 Synechocystis sp.
CrtO
-
 Synechocystis sp.
CrtO ketolase
-
 Synechocystis sp.

Temperature Optimum [°C]

Temperature Optimum [°C] Temperature Optimum Maximum [°C] Comment Organism
28
-
 assay at Synechocystis sp.

pH Optimum

pH Optimum Minimum pH Optimum Maximum Comment Organism
7.8
-
 assay at Synechocystis sp.

Cofactor

Cofactor Comment Organism Structure
quinone
-
 Synechocystis sp.

General Information

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.