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The biosynthesis of oxylipins of linoleic and arachidonic acids by the sewage fungus Leptomitus lacteus , including the identification of 8 R ‐hydroxy‐9 Z ,12 Z ‐octadecadienoic acid
Author(s) -
Fox Simon R.,
Akpinar Arzu,
Prabhune Asmita A.,
Friend John,
Ratledge Colin
Publication year - 2000
Publication title -
lipids
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.601
H-Index - 120
eISSN - 1558-9307
pISSN - 0024-4201
DOI - 10.1007/s11745-000-0490-5
Subject(s) - arachidonic acid , linoleic acid , biosynthesis , biochemistry , biotransformation , metabolite , chemistry , fatty acid , fungus , metabolism , polyunsaturated fatty acid , metabolic pathway , stereochemistry , enzyme , biology , botany
When the sewage fungus Leptomitus lacteus was grown in liquid culture aerobically and then transferred to medium containing long‐chain fatty acids, it produced a number of oxygenated fatty acids. From linoleic acid (18∶2n−6), the major metabolite produced was R ‐8‐hydroxy‐9 Z ,12 Z ‐octadecadienoic acid (8 R ‐HODE), with additional quantities of 8,11‐di‐HODE, 11,16‐di‐HODE, and 11,17‐di‐HODE. Other fatty acid derivatives identified included 7‐HODE, 10‐HODE, and 13‐hydroxy‐octadecamonoenoic acid. Arachidonic acid (20∶4n−6) was metabolized primarily to 18‐ and and 19‐hydroxy‐eicosatetraenoic acids (18‐ and 19‐HETE) also as R enantiomers, along with smaller quantities of 17‐HETE, 9‐HETE, 14,15‐dihydroxyeicosatrienoic acid and 11,12,19‐trihydroxy‐eicosatrienoic acid. The oxygenated products of long‐chain fatty acids, in particular the biosynthesis of 8 R ‐HODE, a compound classified as a precocious sporulation inducer, were similar to those produced by an unrelated fungal species in the Ascomycota, the take‐all fungus Gaeumannomyces graminis . As in G. graminis , the biotransformation of linoleate to 8 R ‐HODE was not significantly inhibited by exposure of the organism to CO. This indicated that the enzyme responsible for 8 R ‐HODE biosynthesis in Leptomitus could be similar to that of G. graminis ; yet we did not detect 7,8‐di‐HODE as a product of 18∶2n−6 metabolism as in G. graminis . CO did inhibit the biosynthesis of 14,15‐di‐HETE, 18‐HETE, and 19‐HETE in L. lacteus , which suggested the involvement of a cytochrome P 450 ‐type monooxygenase. The biosynthesis of 8 R ‐HODE from 18∶2n−6 was found to occur in certain cell lysates, specifically in low speed (15,000× g ) supernatant, following cell disruption.