Oxygenation of Unsaturated Fatty Acids by the Vesicular Gland of Sheep

Abstract

Abstract The products formed on oxygenation of certain unsaturated fatty acids in preparations of sheep vesicular gland have been studied. Oxygenation of linoleic acid yielded 9-hydroxy-10,12-octadecadienoic acid (82%) and 13-hydroxy-9, 11-octadecadienoic acid (18%). Oxygenation of 8,11,14-eicosatrienoic acid yielded 11-hydroxy-8,12,14-eicosatrienoic acid, 15-hydroxy-8,11,13-eicosatrienoic acid, 12-hydroxy-8,10-heptadecadienoic acid, prostaglandin E1 (PGE1), and prostaglandin F1α. The biosynthesis of 12-hydroxy-8,10-heptadecadienoic acid was studied with the use of [2-14C]-, [9-3H,3-14C]-, [10-3H,3-14C]-, [11-3H,2-14C]-, [13d-3H,3-14C]-, [13l-3H,3-14C]-, and [15-3H,3-14C]8,11,14-eicosatrienoic acids. These experiments showed that C-9, C-10, and C-11 are eliminated from the precursor and that the stereochemistry of the removal of hydrogen from C-13 is identical with that occurring during the biosynthesis of PGE1. The 3-carbon compound formed together with 12-hydroxy-8,10-heptadecadienoic acid from 8,11,14-eicosatrienoic acid was identified as malonaldehyde. The identification could be accomplished by condensing malonaldehyde with l-arginine, yielding δ-N-2(pyrimidinyl)-l-ornithine. The mode of formation of 12-hydroxy-8,10-heptadecadie-noic acid and malonaldehyde from 8,11,14-eicosatrienoic acid is discussed. The compounds are proposed to originate in a cyclic peroxide, which has earlier been postulated to be an intermediate in the biosynthesis of prostaglandins.