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Reaction specificities of the ε‐ionone‐forming lycopene cyclase from rice ( Oryza sativa) elucidated in vitro
Author(s) -
Yu Qiuju,
Beyer Peter
Publication year - 2012
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2012.07.060
Subject(s) - lycopene , flavin group , chemistry , cofactor , redox , oryza sativa , ionone , carotenoid , stereochemistry , biochemistry , enzyme , organic chemistry , gene
Lycopene cyclases responsible for the formation of ε‐ionone rings (LCYe) mark a plant‐specific bifurcation of carotenogenesis. We investigated purified rice LCYe (OsLCYe) in a liposome‐based biphasic assay system. OsLCYe depends on reduced flavin cofactors stabilizing a transient state formed during the non‐redox cyclization reaction. In contrast to OsLCYb, OsLCYe produces predominantly monocyclic products and monocyclic carotene intermediates are not suitable substrates. Determination of the OsLCYe reaction specificities and the combined use of OsLCYb allow the characterization of the reaction sequence leading to heterocyclic carotenoids. It was also found that 5‐ cis‐ lycopene, which was thought to be decisive for ε‐cyclization, was not involved in the reaction, with OsLCYe acting as an exclusion filter for this naturally occurring isomer.