EC Number   |
Substrates |
Organism |
Products |
Reversibility |
|---|
   1.17.5.B2 | 4,4'-dihydroxy-beta-carotene + benzoquinone |
via 4-hydroxy-4'-oxo-beta-carotene |
Synechocystis sp. |
canthaxanthin + benzoquinol |
- |
? |
| 1.17.5.B2 | beta-carotene + benzoquinone + H2O |
- |
Synechocystis sp. |
echinenone + benzoquinol + 2 H+ |
- |
? |
| 1.17.5.B2 | more |
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. |
? |
- |
? |
