title: A lycopene β-cyclase/lycopene ε-cyclase/light-harvesting complex-fusion protein from the green alga Ostreococcus lucimarinus can be modified to produce α-carotene and β-carotene at different ratios.
abstract: Biosynthesis of asymmetric carotenoids such as α-carotene and lutein in plants and green algae involves the two enzymes lycopene β-cyclase (LCYB) and lycopene ε-cyclase (LCYE). The two cyclases are closely related and probably resulted from an ancient gene duplication. While in most plants investigated so far the two cyclases are encoded by separate genes, prasinophyte algae of the order Mamiellales contain a single gene encoding a fusion protein comprised of LCYB, LCYE and a C-terminal light-harvesting complex (LHC) domain. Here we show that the lycopene cyclase fusion protein from Ostreococcus lucimarinus catalyzed the simultaneous formation of α-carotene and β-carotene when heterologously expressed in Escherichia coli. The stoichiometry of the two products in E. coli could be altered by gradual truncation of the C-terminus, suggesting that the LHC domain may be involved in modulating the relative activities of the two cyclase domains in the algae. Partial deletions of the linker region between the cyclase domains or replacement of one or both cyclase domains with the corresponding cyclases from the green alga Chlamydomonas reinhardtii resulted in pronounced shifts of the α-carotene-to-β-carotene ratio, indicating that both the relative activities of the cyclase domains and the overall structure of the fusion protein have a strong impact on the product stoichiometry. The possibility to tune the product ratio of the lycopene cyclase fusion protein from Mamiellales renders it useful for the biotechnological production of the asymmetric carotenoids α-carotene or lutein in bacteria or fungi.
authors.affiliation: Institut für Allgemeine Botanik, Johannes Gutenberg-Universität, 55099, Mainz, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Blatt
authors.affiliation: Institut für Allgemeine Botanik, Johannes Gutenberg-Universität, 55099, Mainz, Germany.
authors.forename: Matthias E
authors.initials: ME
authors.lastname: Bauch
authors.affiliation: Institut für Allgemeine Botanik, Johannes Gutenberg-Universität, 55099, Mainz, Germany.
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Pörschke
authors.affiliation: Institut für Allgemeine Botanik, Johannes Gutenberg-Universität, 55099, Mainz, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Lohr
mesh_terms: D002338:Carotenoids / Q000378:metabolism*; D000460:Chlorophyta / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D019753:Intramolecular Lyases / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism*; D019207:beta Carotene / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; D019207:beta Carotene; D002338:Carotenoids; C041635:alpha-carotene; D019753:Intramolecular Lyases; C070925:lycopene cyclase-isomerase
keywords: Bigelowiella natans; Chlamydomonas reinhardtii; Mamiellales; Ostreococcus lucimarinus; carotenoid biosynthesis; light-harvesting complex; lycopene cyclase