Biosynthesis of 8R-hydroperoxylinoleic acid by the fungus Laetisaria arvalis.

8-Hydroxylinoleic acid is known to be a fungicidal metabolite formed by the fungus Laetisaria arvalis (Bowers, W.S. et al. (1986) Science 232, 105-106). In the present report, the mechanism of formation of 8-hydroxylinoleic acid was investigated. L. arvalis metabolized [14C]linoleic acid to 8-hydroperoxylinoleic acid and 8-hydroxylinoleic acid as major metabolites. The identification is based on the reduction of the hydroperoxide to an alcohol with stannous chloride and gas chromatography-mass spectrometry. The absolute configuration of the hydroxyl was determined to be R by ozonolysis of the (-)-menthoxycarbonyl derivative of 8-hydroxylinoleic acid. Linoleic acid 8R-dioxygenase activity was present in the 100,000 x g supernatant of the cell lysate. In summary, the 8R-linoleic acid dioxygenase of L. arvalis shows many similarities with the 8R-dioxygenase recently described in the fungus Gaeumannomyces graminis.