Heterologous production of two unusual acyclic carotenoids, 1,1'-dihydroxy-3,4-didehydrolycopene and 1-hydroxy-3,4,3',4'-tetradehydrolycopene by combination of the crtC and crtD genes from Rhodobacter and Rubrivivax.

Acyclic hydroxy carotenoids were produced from lycopene and 3,4-didehydrolycopene in Escherichia coli by combining different carotenogenic genes including the carotene hydratase gene crtC and the carotene 3,4-desaturase gene crtD. The genes originated either from Rhodobacter species or Rubrivivax gelatinosus. It was shown that the product of crtD from Rubrivivax unlike the one from Rhodobacter is able to convert 1-HO-3,4-didehydrolycopene to 1-HO-3,4,3',4'-tetradehydrolycopene (=3,4,3',4'-tetradehydro-1,2-dihydro-psi,psi-caroten-1-ol). Thus, only when the desaturase from Rubrivivax is expressed can this novel carotenoid be obtained. In the presence of crtC from Rubrivivax, another carotenoid 1,1'-(HO)(2)-3,4-didehydrolycopene (=3,4-didehydrolycopene-1,2,1',2'-tetrahydro-psi,psi-caroten-1,1'-diol) not found in a non-transgenic organism before is formed in E. coli. Its accumulation under these conditions and its absence when crtC from Rubrivivax is replaced by the corresponding gene from Rhodobacter is discussed. The function of the different crtC and crtD genes in the pathway leading to the individual carotenoids is outlined. Since 1,1'-(HO)(2)-3,4-didehydrolycopene could not be produced in substantial amounts and 1-HO-3,4,3',4'-tetradehydrolycopene has not been described before, their structural characteristics were determined for the definite assignment of their identity. This included spectral properties, determination of relative molecular mass as well as the number of hydroxy groups by mass spectroscopy and NMR spectroscopy for 1,1'-(HO)(2)-3,4-didehydrolycopene.