title: Cloning and characterization of genes involved in nostoxanthin biosynthesis of Sphingomonas elodea ATCC 31461.
abstract: Most Sphingomonas species synthesize the yellow carotenoid nostoxanthin. However, the carotenoid biosynthetic pathway of these species remains unclear. In this study, we cloned and characterized a carotenoid biosynthesis gene cluster containing four carotenogenic genes (crtG, crtY, crtI and crtB) and a β-carotene hydroxylase gene (crtZ) located outside the cluster, from the gellan-gum producing bacterium Sphingomonas elodea ATCC 31461. Each of these genes was inactivated, and the biochemical function of each gene was confirmed based on chromatographic and spectroscopic analysis of the intermediates accumulated in the knockout mutants. Moreover, the crtG gene encoding the 2,2'-β-hydroxylase and the crtZ gene encoding the β-carotene hydroxylase, both responsible for hydroxylation of β-carotene, were confirmed by complementation studies using Escherichia coli producing different carotenoids. Expression of crtG in zeaxanthin and β-carotene accumulating E. coli cells resulted in the formation of nostoxanthin and 2,2'-dihydroxy-β-carotene, respectively. Based on these results, a biochemical pathway for synthesis of nostoxanthin in S. elodea ATCC 31461 is proposed.
authors.affiliation: Institute of Microbiology, College of Life Sciences, Zhejiang University, Hangzhou, Zhejiang, People's Republic of China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhu
authors.forename: Xuechang
authors.initials: X
authors.lastname: Wu
authors.forename: Ou
authors.initials: O
authors.lastname: Li
authors.forename: Chaodong
authors.initials: C
authors.lastname: Qian
authors.forename: Haichun
authors.initials: H
authors.lastname: Gao
mesh_terms: D004926:Escherichia coli; D055786:Gene Knockout Techniques; D053858:Metabolic Networks and Pathways / Q000235:genetics; D006899:Mixed Function Oxygenases / Q000096:biosynthesis / Q000235:genetics* / Q000302:isolation & purification; D009154:Mutation; D010802:Phylogeny; D017421:Sequence Analysis; D020578:Sphingomonas / Q000201:enzymology* / Q000235:genetics*; D024341:Xanthophylls / Q000096:biosynthesis / Q000235:genetics*; D019207:beta Carotene / Q000235:genetics* / Q000378:metabolism
chemical_list: D024341:Xanthophylls; C533811:nostoxanthin; D019207:beta Carotene; D006899:Mixed Function Oxygenases