title: Copper-Induced Inactivation of Camel Liver Glutathione S-Transferase.
abstract: Glutathione S-transferases (GSTs) are multifunctional enzymes and play an important role in detoxification of xenobiotics and protection against oxidative stress. Camel liver glutathione transferase (cGST) was recently isolated and characterized in our lab. In this study, we have evaluated the effect of monovalent, divalent, and trivalent cations on its activity and stability. Cu(++) was found to be the potent inhibitor of GST activity which loses complete activity at 0.5-mM concentration. Other metal ions did not inhibit GST even at higher concentration of 2 mM. GST incubated with Cu(++) (0.1 mM) resulted decrease in free sulfhydryl groups by 55%, whereas other metal ions did not show any effect on free thiol content. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis showed formation of GST aggregates instantly in the presence of Cu(++), which further increased in molecular size with increase in time of incubation. DTT treatment resulted in de-aggregation of GST oligomers to its monomeric form. However, the GST activity was not recovered completely after de-aggregation. Cu(++) was found to inhibit GST activity by accelerating the inter- and intra-disulfide bond formation. Far-UV circular dichroism (CD) results showed that Cu(++)-catalyzed air oxidation of sulfhydryl groups leads to minor conformational changes in the GST.
authors.affiliation: Protein Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia. anahmed@ksu.edu.sa.|Center of Excellence in Biotechnology Research, Department of Biochemistry, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia. anahmed@ksu.edu.sa.
authors.forename: Anwar
authors.initials: A
authors.lastname: Ahmed
authors.affiliation: Protein Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
authors.forename: Ajamaluddin
authors.initials: A
authors.lastname: Malik
authors.affiliation: Protein Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
authors.forename: Haseeb
authors.initials: H
authors.lastname: Jagirdar
authors.affiliation: Protein Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
authors.forename: Nayyar
authors.initials: N
authors.lastname: Rabbani
authors.affiliation: Protein Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
authors.forename: Mohd Shahnawaz
authors.initials: MS
authors.lastname: Khan
authors.affiliation: Protein Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
authors.forename: Abdulrahman M
authors.initials: AM
authors.lastname: Al-Senaidy
authors.affiliation: Protein Research Chair, Department of Biochemistry, College of Science, King Saud University, Riyadh, 11451, Saudi Arabia.
authors.forename: Mohamed A
authors.initials: MA
authors.lastname: Ismael
mesh_terms: D000818:Animals; D002162:Camelus; D003300:Copper / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D005982:Glutathione Transferase / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D018384:Oxidative Stress / Q000187:drug effects
chemical_list: D003300:Copper; D005982:Glutathione Transferase
keywords: Aggregation; Copper; Glutathione S-transferases; Metal ions; Thiol groups