THE CAROTENOID 7,8-DIHYDRO-PSI END GROUP CAN BE CYCLIZED BY THE LYCOPENE CYCLASES FRONT THE BACTERIUM ERWINIA-UREDOVORA AND THE HIGHER-PLANT CAPSICUM-ANNUUM

The genes for geranylgeranyl diphosphate synthase (crtE) and phytoene synthase (crtB) from the epiphytic bacterium Erwinia uredovora and the phytoene desaturase gene from the photosynthetic bacterium Rhodobacte r capsulatus (Rc-crtI) were introduced into Escherichia coli, which re sulted in the accumulation of the acyclic carotenoid, neurosporene. Fu rther introduction of the lycopene cyclase gene from E. uredovora a (c rtY) or the higher plant Capsicum annuum (Icy) resulted in the product ion of a bicyclic carotenoid, 7,8-dihydro-beta-carotene, via monocycli c beta-zeacarotene. xi-Carotene was also found to be cyclized to bicyc lic 7,8,7',8'-tetrahydro-beta-carotene by the Erwinia cyclase. These r esults indicate that both lycopene cyclases can cyclize a 7,8-dihydro- Psi end group to a 7,8-dihydro-beta end group, in addition to the usua l cyclization of the Psi end group to the beta end group. Furthermore, beta-carotene hydroxylase from Erwinia (CrtZ) was able to add a hydro xyl group to the 7,8-dihydro-beta end group and the beta end group.