title: Tomato CYP74C3 is a multifunctional enzyme not only synthesizing allene oxide but also catalyzing its hydrolysis and cyclization.
abstract: The mechanism of the recombinant tomato allene oxide synthase (LeAOS3, CYP74C3) was studied. Incubations of linoleic acid (9S)-hydroperoxide with dilute suspensions of LeAOS3 (10-20 s, 0 degrees C) yield mostly the expected allene oxide (12Z)-9,10-epoxy-10,12-octadecadienoic acid (9,10-EOD), which was detected as its methanol-trapping product. In contrast, the relative yield of 9,10-EOD progressively decreased when the incubations were performed with fourfold, tenfold, or 80-fold larger amounts of LeAOS3, while alpha-ketol and the cyclopentenone rac-cis-10-oxo-11-phytoenoic acid (10-oxo-PEA) became the predominant products. Both the alpha-ketol and 10-oxo-PEA were also produced when LeAOS3 was exposed to preformed 9,10-EOD, which was generated by maize allene oxide synthase (CYP74A). LeAOS3 also converted linoleic acid (13S)-hydroperoxide into the corresponding allene oxide, but with about tenfold lower yield of cyclopentenone. The results indicate that in contrast to the ordinary allene oxide synthases (CYP74A subfamily), LeAOS3 (CYP74C subfamily) is a multifunctional enzyme, catalyzing not only the synthesis, but also the hydrolysis and cyclization of allene oxide.
authors.affiliation: Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, Kazan, Russia. grechkin@mail.knc.ru
authors.forename: Alexander N
authors.initials: AN
authors.lastname: Grechkin
authors.forename: Lucia S
authors.initials: LS
authors.lastname: Mukhtarova
authors.forename: Larisa R
authors.initials: LR
authors.lastname: Latypova
authors.forename: Yuri
authors.initials: Y
authors.lastname: Gogolev
authors.forename: Yana Y
authors.initials: YY
authors.lastname: Toporkova
authors.forename: Mats
authors.initials: M
authors.lastname: Hamberg
mesh_terms: D000475:Alkenes / Q000737:chemistry / Q000378:metabolism; D055162:Biocatalysis; D002851:Chromatography, High Pressure Liquid; D003500:Cyclization; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D006868:Hydrolysis; D019746:Intramolecular Oxidoreductases / Q000378:metabolism*; D018551:Solanum lycopersicum / Q000201:enzymology*; D009682:Magnetic Resonance Spectroscopy; D013058:Mass Spectrometry; D000432:Methanol / Q000737:chemistry / Q000378:metabolism; D015394:Molecular Structure; D010940:Plant Proteins / Q000378:metabolism*; D013379:Substrate Specificity; D003313:Zea mays / Q000201:enzymology
chemical_list: D000475:Alkenes; D010940:Plant Proteins; D003577:Cytochrome P-450 Enzyme System; D019746:Intramolecular Oxidoreductases; C021377:hydroperoxide isomerase; D000432:Methanol