A carotenoid synthesis gene cluster from Algoriphagus sp. KK10202C with a novel fusion-type lycopene beta-cyclase gene.

A carotenoid synthesis gene cluster was isolated from a marine bacterium Algoriphagus sp. strain KK10202C that synthesized flexixanthin. Seven genes were transcribed in the same direction, among which five of them were involved in carotenoid synthesis. This cluster had a unique gene organization, with an isoprenoid gene, ispH (previously named lytB), being present among the carotenoid synthesis genes. The lycopene beta-cyclase encoded by the crtY ( cd ) gene appeared to be a fusion of bacterial heterodimeric lycopene cyclase CrtY(c) and CrtY(d). This was the first time that a fusion-type of lycopene beta-cyclase was reported in eubacteria. Heterologous expression of the Algoriphagus crtY ( cd ) gene in lycopene-accumulating Escherichia coli produced bicyclic beta-carotene. A biosynthesis pathway for monocyclic flexixanthin was proposed in Algoriphagus sp. strain KK10202C, though several of the carotenoid synthesis genes not linked with the cluster have not yet been cloned.