Metabolism of oxidized linoleic acid by glutathione transferases: Peroxidase activity toward 13-hydroperoxyoctadecadienoic acid Stacy K. Seeley a , Julie A. Poposki b , John Maksimchuk a , Jill Tebbe a , Jon Gaudreau a , Bengt Mannervik c , Arthur W. Bull b, ⁎ a Department of Science and Math, Kettering University, Flint, MI 48504, USA b Department of Chemistry, Oakland University, Rochester, MI 48309-4477, USA c Department of Biochemistry, Uppsala University, SE-751 23 Uppsala, Sweden Received 3 January 2006; received in revised form 18 February 2006; accepted 22 February 2006 Available online 31 March 2006 Abstract The oxidation of linoleic acid produces several products with biological activity including the hydroperoxy fatty acid 13- hydroperoxyoctadecadienoic acid (13-HPODE), the hydroxy fatty acid 13-hydroxyoctadecadienoic acid (13-HODE), and the 2,4-dienone 13- oxooctadecadienoic acid (13-OXO). In the present work, the peroxidase activity of glutathione transferases (GST) A1-1, M1-1, M2-2, and P1-1 (Val 105) toward 13-HPODE has been examined. The alpha class enzyme is the most efficient peroxidase while the two enzymes from the mu class exhibit weak peroxidase activity toward 13-HPODE. It was also determined that the conjugated diene 13-HODE is not a substrate for GST from the alpha and mu classes but that 13-HODE does inhibit the GST-catalyzed conjugation of CDNB by enzymes from the alpha, mu, and pi classes. Finally, both 13-HODE and 13-OXO were shown to be inducers of GSTactivity in HT-29 and HCT-116 colon tumor cells. These data help to clarify the role of GST in the metabolic disposition of linoleic acid oxidation products. © 2006 Elsevier B.V. All rights reserved. Keywords: Glutathione transferase; 13-HODE; 13-HPODE; Oxidized linoleic acid metabolism; Enzyme induction 1. Introduction The oxidative metabolism of linoleic acid produces a number of bioactive products including 13-hydroperoxyoctadeca-9,11- dienoic acid (13-HPODE), 13-hydroxyoctadeca-9,11-dienoic acid (13-HODE), and the 2,4-dienone 13-oxooctadeca-9,11- dienoic acid (13-OXO). Removal of linoleate oxidation products from cells is mediated, in part, by the glutathione transferase (GST)-dependent conjugation of 13-OXO followed by export of the 13-OXO-glutathione (13-OXO-SG) conjugate [1,2]. This metabolic pathway is summarized in Fig. 1. The bioactive compounds are involved in a number of important processes including growth factor signal transduction and cellular differentiation [3–7]. As a result, a determination of the metabolic disposition of these products is important for understanding the normal and pathological responses mediated by linoleate oxygenation [8–12]. The GSTs are known to play a role in the metabolic disposition of distal linoleate oxidation products such as 13- OXO [1]. In particular, one metabolic fate of 13-OXO is conjugation with glutathione (GSH) to form 13-OXO-SG prior to energy-dependent export out of the cell [1,2]. Still unanswered is the question of whether GSTs are also able to catalyze the conjugation of 13-HODE with GSH. The conjugated diene moiety of 13-HODE suggests it would be a reasonable candidate as a GST substrate and such an activity would have implications for the response of tissues to linoleate oxygenation. The formation of fatty acid hydroperoxides occurs in both normal and disease states. As the hydroperoxy compounds are chemically unstable and prone to chain reaction decomposition processes, cellular peroxidases have evolved to reduce the hydroperoxides to more stable hydroxy species. The peroxidase activity of GST toward organic hydroperoxides was first characterized in rat liver [13]. In humans, this activity is Biochimica et Biophysica Acta 1760 (2006) 1064 – 1070 http://www.elsevier.com/locate/bba ⁎ Corresponding author. Tel.: +1 248 370 2347; fax: +1 248 370 2321. E-mail address: abull@oakland.edu (A.W. Bull). 0304-4165/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.bbagen.2006.02.020