出版社：American Society for Biochemistry and Molecular Biology
摘要：Seven Z -octadecenoic acids having the double bond located in positions 6Z to 13Z were photooxidized. The resulting hydroperoxy- E -octadecenoic acids [HpOME( E )] were resolved by chiral phase-HPLC-MS, and the absolute configurations of the enantiomers were determined by gas chromatographic analysis of diastereoisomeric derivatives. The MS/MS/MS spectra showed characteristic fragments, which were influenced by the distance between the hydroperoxide and carboxyl groups. These fatty acids were then investigated as substrates of cyclooxygenase-1 (COX-1), manganese lipoxygenase (MnLOX), and the (8 R )-dioxygenase (8 R -DOX) activities of two linoleate diol synthases (LDS) and 10 R -DOX. COX-1 and MnLOX ed hydrogen at C-11 of (12 Z ) - 18:1 and C-12 of (13 Z ) - 18:1. (11 Z ) - 18:1 was subject to hydrogen ion at C-10 by MnLOX and at both allylic positions by COX-1. Both allylic hydrogens of (8 Z ) - 18:1 were also ed by 8 R -DOX activities of LDS and 10 R -DOX, but only the allylic hydrogens close to the carboxyl groups of (11 Z ) - 18:1 and (12 Z ) - 18:1. 8 R -DOX also oxidized monoenoic C14-C20 fatty acids with double bonds at the (9 Z ) position, suggesting that the length of the omega end has little influence on positioning for oxygenation. We conclude that COX-1 and MnLOX can readily allylic hydrogens of octadecenoic fatty acids from C-10 to C-12 and 8 R -DOX from C-7 and C-12.
