Biosynthesis of 12-oxo-10,15(Z)-phytodienoic acid: identification of an allene oxide cyclase.
Incubation of 13(S)-hydroperoxy-9(Z),11(E),15(Z)-octadecatrienoic acid with corn (Zea mays L.) hydroperoxide dehydrase led to the formation of an unstable allene oxide derivative, 12,13(S)-epoxy-9(Z),11,15(Z)-octadecatrienoic acid. Further conversion of the allene oxide yielded two major products, i.e. alpha-ketol 12-oxo-13-hydroxy-9(Z),15(Z)-octadecadienoic acid, and 12-oxo-10,15(Z)-phytodienoic acid (12-oxo-PDA). 12-Oxo-PDA was formed from allene oxide by two different pathways, i.e. spontaneous chemical cyclization, leading to racemic 12-oxo-PDA, and enzyme-catalyzed cyclization, leading to optically pure 12-oxo-PDA. The allene oxide cyclase, a novel enzyme in the metabolism of oxygenated fatty acids, was partially characterized and found to be a soluble protein with an apparent molecular weight of about 45,000 that specifically catalyzed conversion of allene oxide into 9(S),13(S)-12-oxo-PDA.
Hamberg
M
M
Department of Physiological Chemistry, Karolinska Institutet, Stockholm, Sweden.
D005231:Fatty Acids, Unsaturated / Q000096:biosynthesis*; D006836:Hydro-Lyases / Q000302:isolation & purification; D019746:Intramolecular Oxidoreductases; D007535:Isomerases / Q000302:isolation & purification / Q000378:metabolism*; D007700:Kinetics; D008042:Linolenic Acids / Q000378:metabolism; D008054:Lipid Peroxides / Q000378:metabolism; D010944:Plants / Q000378:metabolism*; D013237:Stereoisomerism; D003313:Zea mays / Q000378:metabolism
D005231:Fatty Acids, Unsaturated; D008042:Linolenic Acids; D008054:Lipid Peroxides; C057375:13-hydroperoxy-9,11,15-octadecatrienoic acid; C025999:12-oxophytodienoic acid; D006836:Hydro-Lyases; C057374:hydroperoxide dehydratase; D007535:Isomerases; D019746:Intramolecular Oxidoreductases; C021377:hydroperoxide isomerase