Biochemical Characterization and Distribution of Glutathione S-Transferases in Leaping Mullet (Liza saliens)

A. Sen^* and A. Kirikbakan

Department of Biology, Pamukkale University, 20017 Kinikli-Denizli, Turkey; fax: 90-258-212-5546; E-mail: sena@pamukkale.edu.tr

^* To whom correspondence should be addressed.

¹ Part of this work was presented at the 13th International Conference “Cytochromes P450. Biochemistry, Biophysics and Drug Metabolism”, June 29-July 3, 2003, Prague, Czech Republic.

Received January 14, 2004; Revision received February 27, 2004

---

In this study, feral leaping mullet (Liza saliens) liver cytosolic glutathione S-transferases (GSTs) were investigated and characterized using 1-chloro-2,4-dinitrobenzene (CDNB) and ethacrynic acid (EA) as substrates. The average GST activities towards CDNB and EA were found to be 1365 ± 41 and 140 ± 20 nmol/min per mg protein, respectively. The effects of cytosolic protein amount and temperature ranging from 4 to 70°C on enzyme activities were examined. While both activities towards CDNB and EA showed similar dependence on protein amount, temperature optima were found as 37 and 42°C, respectively. In addition, the effects of pH on GST-CDNB and -EA activities were studied and different pH activity profiles were observed. For both substrates, GST activities were found to obey Michaelis-Menten kinetics with apparent V_max and K_m values of 1661 nmol/min per mg protein and 0.24 mM and 157 nmol/min per mg protein and 0.056 mM for CDNB and EA, respectively. Distribution of GST in Liza saliens tissues was investigated and compared with other fish species. Very high GST activities were measured in tissues from Liza saliens such as liver, kidney, testis, proximal intestine, and gills. Moreover, our results suggested that GST activities from Liza saliens would be a valuable biomarker for aquatic pollution.

---

KEY WORDS: phase II, glutathione S-transferases, 1-chloro-2,4-dinitrobenzene, ethacrynic acid, biomonitoring, Liza saliens

---