A new class of fatty acid allene oxide formed by the DOX-P450 fusion proteins of human and plant pathogenic fungi, C. immitis and Z. tritici.
Linoleate dioxygenase-cytochrome P450 (DOX-CYP) fusion enzymes are common in pathogenic fungi. The DOX domains form hydroperoxy metabolites of 18:2n-6, which can be transformed by the CYP domains to 1,2- or 1,4-diols, epoxy alcohols, or to allene oxides. We have characterized two novel allene oxide synthases (AOSs), namely, recombinant 8R-DOX-AOS of Coccidioides immitis (causing valley fever) and 8S-DOX-AOS of Zymoseptoria tritici (causing septoria tritici blotch of wheat). The 8R-DOX-AOS oxidized 18:2n-6 sequentially to 8R-hydroperoxy-9Z,12Z-octadecadienoic acid (8R-HPODE) and to an allene oxide, 8R(9)-epoxy-9,12Z-octadecadienoic acid, as judged from the accumulation of the α-ketol, 8S-hydroxy-9-oxo-12Z-octadecenoic acid. The 8S-DOX-AOS of Z. tritici transformed 18:2n-6 sequentially to 8S-HPODE and to an α-ketol, 8R-hydroxy-9-oxo-12Z-octadecenoic acid, likely formed by hydrolysis of 8S(9)-epoxy-9,12Z-octadecadienoic acid. The 8S-DOX-AOS oxidized [8R-(2)H]18:2n-6 to 8S-HPODE with retention of the (2)H-label, suggesting suprafacial hydrogen abstraction and oxygenation in contrast to 8R-DOX-AOS. Both enzymes oxidized 18:1n-9 and 18:3n-3 to α-ketols, but the catalysis of the 8R- and 8S-AOS domains differed. 8R-DOX-AOS transformed 9R-HPODE to epoxy alcohols, but 8S-DOX-AOS converted 9S-HPODE to an α-ketol (9-hydroxy-10-oxo-12Z-octadecenoic acid) and epoxy alcohols in a ratio of ∼1:2. Whereas all fatty acid allene oxides described so far have a conjugated diene impinging on the epoxide, the allene oxides formed by 8-DOX-AOS are unconjugated.
Division of Biochemical Pharmacology, Department of Pharmaceutical Biosciences, Uppsala University, SE-751 24 Uppsala, Sweden Ernst.oliw@farmbio.uu.se.
Ernst H
EH
Oliw
Division of Biochemical Pharmacology, Department of Pharmaceutical Biosciences, Uppsala University, SE-751 24 Uppsala, Sweden.
Marc
M
Aragó
Division of Biochemical Pharmacology, Department of Pharmaceutical Biosciences, Uppsala University, SE-751 24 Uppsala, Sweden.
Yang
Y
Chen
Division of Biochemical Pharmacology, Department of Pharmaceutical Biosciences, Uppsala University, SE-751 24 Uppsala, Sweden.
Fredrik
F
Jernerén
D016718:Arachidonic Acid / Q000737:chemistry / Q000378:metabolism; D001203:Ascomycota / Q000201:enzymology*; D055162:Biocatalysis; D003045:Coccidioides / Q000201:enzymology*; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry* / Q000502:physiology; D005656:Fungal Proteins / Q000737:chemistry* / Q000502:physiology; D006801:Humans; D006868:Hydrolysis; D019746:Intramolecular Oxidoreductases / Q000737:chemistry* / Q000502:physiology; D010084:Oxidation-Reduction; D011993:Recombinant Fusion Proteins / Q000737:chemistry
D005656:Fungal Proteins; D011993:Recombinant Fusion Proteins; D016718:Arachidonic Acid; D003577:Cytochrome P-450 Enzyme System; D019746:Intramolecular Oxidoreductases; C021377:hydroperoxide isomerase
8-dioxygenase; Coccidioides immitis; Zymoseptoria tritici; cyclooxygenase; cytochrome P450 74 family; dioxygenase; lipid metabolism; lipidomics; oxygenation mechanism