US EPA

1046419 

Journal Article 

Tomato CYP74C3 is a multifunctional enzyme not only synthesizing allene oxide but also catalyzing its hydrolysis and cyclization 

Grechkin, AN; Mukhtarova, LS; Latypova, LR; Gogolev, Y; Toporkova, YY; Hamberg, M 

2008 

Yes 

ChemBiochem
ISSN: 1439-4227
EISSN: 1439-7633 

9 

15 

2498-2505 

English 

18780387 

10.1002/cbic.200800331 

WOS:000260591100020 

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. 

allene oxide synthase; enzyme catalysis; metabolism; oxylipins; tomato