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Analysis of novel hydroperoxides and other metabolites of oleic, linoleic, and linolenic acids by liquid chromatography‐mass spectrometry with ion trap MS n
Author(s) -
Oliw Ernst H.,
Su Chao,
Skogström Torun,
Benthin Günther
Publication year - 1998
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/s11745-998-0280-0
Subject(s) - chemistry , mass spectrometry , chromatography , oleic acid , linoleic acid , linolenic acid , ion trap , metabolite , fast atom bombardment , gas chromatography , fatty acid , biochemistry
Linoleate is oxygenated by manganese‐lipoxygenase (Mn‐LO) to 11 S ‐hydroperoxylinoleic acid and 13 R ‐hydroperoxyoctadeca‐9 Z ,11 E ‐dienoic acid, whereas linoleate diol synthase (LDS) converts linoleate sequentially to 8 R ‐hydroperoxylinoleate, through an 8‐dioxygenase by insertion of molecular oxygen, and to 7 S ,8 S ‐dihydroxylinoleate, through a hydroperoxide isomerase by intramolecular oxygen transfer. We have used liquid chromatography‐mass spectrometry (LC‐MS) with an ion trap mass spectrometer to study the MS n mass spectra of the main metabolites of oleic, linoleic, α‐linolenic and γ‐linolenic acids, which are formed by Mn‐LO and by LDS. The enzymes were purified from the culture broth (Mn‐LO) and mycelium (LDS) of the fungus Gaeumannomyces graminis . MS 3 analysis of hydroperoxides and MS 2 analysis of dihydroxy‐ and monohydroxy metabolites yielded many fragments with information on the position of oxygenated carbons. Mn‐LO oxygenated C‐11 and C‐13 of 18∶2n−6, 18∶3n−3, and 18∶3n−6 in a ratio of ∼1∶1–3 at high substrate concentrations. 8‐Hydroxy‐9(10)expoxystearate was identified as a novel metabolite of LDS and oleic acid by LC‐MS and by gas chromatography‐MS. We conclude that LC‐MS with MS n is a convenient tool for detection and identification of hydroperoxy fatty acids and other metabolites of these enzymes.