title: Characterization of two beta-carotene ketolases, CrtO and CrtW, by complementation analysis in Escherichia coli.
abstract: The pathways from beta-carotene to astaxanthin are crucial key steps for producing astaxanthin, one of industrially useful carotenoids, in heterologous hosts. Two beta-carotene ketolases (beta-carotene 4,4'-oxygenase), CrtO and CrtW, with different structure are known up to the present. In this paper, we compared the catalytic functions of a CrtO ketolase that was obtained from a marine bacterium Rhodococcus erythropolis strain PR4, CrtO derived from cyanobacterium Synechosistis sp. PCC6803, and CrtW derived from a marine bacterium Brevundimonas sp. SD212, by complementation analysis in Escherichia coli expressing the known crt genes. Results strongly suggested that a CrtO-type ketolase was unable to synthesize astaxanthin from zeaxanthin, i.e., only a CrtW-type ketolase could accept 3-hydroxy-beta-ionone ring as the substrate. Their catalytic efficiency for synthesizing canthaxanthin from beta-carotene was also examined. The results obtained up to the present clearly suggest that the bacterial crtW and crtZ genes are a combination of the most promising gene candidates for developing recombinant hosts that produce astaxanthin as the predominant carotenoid.
authors.affiliation: Marine Biotechnology Institute, Heita, Kamaishi-shi, Iwate 026-0001, Japan.
authors.forename: Seon-Kang
authors.initials: SK
authors.lastname: Choi
authors.forename: Hisashi
authors.initials: H
authors.lastname: Harada
authors.forename: Satoru
authors.initials: S
authors.lastname: Matsuda
authors.forename: Norihiko
authors.initials: N
authors.lastname: Misawa
mesh_terms: D042063:Caulobacteraceae / Q000201:enzymology / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics*; D005816:Genetic Complementation Test; D010105:Oxygenases / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D012240:Rhodococcus / Q000201:enzymology / Q000235:genetics; D046939:Synechocystis / Q000201:enzymology / Q000235:genetics; D019207:beta Carotene / Q000096:biosynthesis
chemical_list: D019207:beta Carotene; D010105:Oxygenases; C093259:beta-carotene ketolase