1-Hydroxy monocyclic carotenoid 3,4-dehydrogenase from a marine bacterium that produces myxol

A crtD (1-HO carotenoid 3,4-dehydrogenase gene) homolog from marine bacterium strain P99-3 included in the gene cluster for the biosynthesis of myxol (3',4'-didehydro-1',2'-dihydro-beta, psi-carotene-3,1',2'-triol) was functionally identified. The P99-3 CrtD was phylogenetically distant from the other CrtDs. A catalytic feature was its high activity for the monocyclic carotenoid conversion: 1'-HO-torulene (3',4'-didehydro-1',2'-dihydro- beta, psi-caroten-1'-ol) was prominently formed from 1'-HO-gamma-carotene (1',2'-dihydro-beta, psi-caroten-1'-ol) in Escherichia coli with P99-3 CrtD, indicating that this enzyme has been highly adapted to myxol biosynthesis. This unique type of crtD is a valuable tool for obtaining 1'-HO-3',4'-didehydro monocyclic carotenoids in a heterologous carotenoid production system.