Novel glutathione conjugates formed from epoxyeicosatrienoic acids (EETs)

The catalysis of glutathione (GSH) conjugation to epoxyeicosatrienoic acids (EETs) by various purified isozymes of glutathione S-transferase was studied. A GSH conjugate of 14,15-EET was isolated by HPLC and TLC; this metabolite contained one molecule of EET and one molecule of GSH. Fast atom bombardment mass spectrometry of the isolated metabolite confirmed the structure as a GSH conjugate of 14,15-EET. Studies designed to determine the isozyme specificity of this reaction demonstrated that two isozymes, 3-3, and 5-5, efficiently catalyzed this conjugation reaction. The Km values for 14,15-EET were approximately 10 microM and the Vmax values ranged from 25 to 60 nmol conjugate formed min-1 mg-1 purified transferase 3-3 and 5-5. The 5,6-, 8,9-, and 11,12-EETs were also substrates for the reaction, albeit at lower rates. These results demonstrate that the EETs can serve as substrates for the cytosolic glutathione S-transferases.