The carotenoid 7,8-dihydro-psi end group can be cyclized by the lycopene cyclases from the bacterium Erwinia uredovora and the higher plant Capsicum annuum.

Abstract

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 Rhodobacter capsulatus (Rc-crtI) were introduced into Escherichia coli, which resulted in the accumulation of the acyclic carotenoid, neurosporene. Further introduction of the lycopene cyclase gene from E. uredovora (crtY) or the higher plant Capsicum annuum (Icy) resulted in the production of a bicyclic carotenoid, 7,8-dihydro-beta-carotene, via monocyclic beta-zeacarotene. zeta-Carotene was also found to be cyclized to bicyclic 7,8,7',8'-tetrahydro-beta-carotene by the Erwinia cyclase. These results 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 usual cyclization of the psi end group to the beta end group. Furthermore, beta-carotene hydroxylase from Erwinia (CrtZ) was able to add a hydroxyl group to the 7,8-dihydro-beta end group and the beta end group.