J. Biol. Chem., Vol. 255, Issue 19, 9001-9004, Oct, 1980
Transformation of arachidonic acid into an iodolactone by the rat thyroid
JM Boeynaems and WC Hubbard
In the presence of iodide and hydrogen peroxide, lactoperoxidase, an enzyme
model for thyroid peroxidase, catalyzed the conversion of arachidonic acid
into several iodinated products. The major product was identified as
6-iodo-5-hydroxy-eicosatrienoic acid, delta-lactone (iodolactone), on the
basis of 125I incorporation, mass spectrometry, proton magnetic resonance
spectroscopy, and chemical modifications. Using this compound as a
standard, two methods were developed to establish and quantitate the
production of iodolactone by the rat thyroid in vitro: 125I labeling
followed by reversed phase high pressure liquid chromatography and combined
gas chromatography-mass spectrometry. Addition of iodide and arachidonic
acid to rat thyroid lobes resulted in the formation and release of the
iodolactone, which was inhibited by methimazole. These data suggest that
peroxidases capable of oxidizing halides could provide a new pathway of
arachidonic acid metabolism, besides cyclooxygenase and lipoxygenases.
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