Calorimetric Studies on the Interaction between two n-alkyl Xanthates and Mushroom Tyrosinase

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Calorimetric Studies on the Interaction between two n-alkyl Xanthates and Mushroom Tyrosinase

Author Affiliations

¹Department of Chemistry, Imam Khomeini International University, Qazvin, IRAN
²Department of Chemistry, Faculty of science, Islamic Azad University, Takestan branch, Takestan, IRAN
³Institute of Biochemistry and Biophysics, University of Tehran, Tehran, IRAN

Res.J.chem.sci., Volume 2, Issue (9), Pages 90-92, September,18 (2012)

Abstract

Thermodynamics of the interaction between two iso-alkyl dithiocarbonates (xanthates), C₃H₇OCS₂Na (I), C₅H₁₁OCS₂Na (II) with mushroom tyrosinase was investigated at 27°C, pH 6.8 and in phosphate buffer (10 mM) by isothermal titration calorimetry to clarify thermodynamics of this binding as well as structural changes of the enzyme due to its interaction with xanthates. These compounds are potent inhibitors of MT with K values of 9.07 x 10⁴, 1.68 x 10⁵ M^-1 for I and II, respectively. The MT inhibition is related to the chelating of the copper ions at the active site by a negative head group (S-) of the anion xanthate. Different K_a values for MT inhibition are related to different interactions of the aliphatic chains of I and II with hydrophobic pockets in the active site of the enzyme. The obtained results indicate that there are two identical and non-cooperative binding sites for both xanthates. The extended solvation theory was used to elucidate the effect of these xanthates on the stability of enzyme. These compounds are potent inhibitors of MT with association equilibrium constant (K_a) values of 9.0710 and 1.68×10⁵ L.mol^-1 for I and II, respectively. Different K values for MT inhibition are related to different interactions of the aliphatic chains of I and II with hydrophobic pockets in the active site of the enzyme. It is possible to ascribe the values of A and for I and II to the type of inhibition. The obtained results indicate that there are two identical and non-cooperative binding sites for both xanthates.

References

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Rezaei Behbehani G., Saboury A.A., Barzegar L., Zarean O., Abedini J. and Payehghdr M., A thermodynamic study on the interaction of nickel with myelin basic protein by isothermal titration calorimetry, J. Therm. Anal. Cal., 101(1), 379-384 (2010)
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[ref1] Sánchez-Ferrer A., Rodríguez-Lopez J.N., Garcia-Canovas F. and Garcia-Carmona F., Tyrosinase: a comprehensive review of its mechanism, J. Biochim Biophys Acta., 1247(1), 1-11 (1995)

[ref2] Korner A.M., and Pawelek J.M., Mammalian tyrosinase catalyzes three reactions in the biosynthesis of melanin, J. Science, 217, 1163–1165 (1982)

[ref3] Saboury A.A., Enzyme Inhibition and Activation: A general theory, J. Iran. Chem. Soc., 6(2), 219-229 (2009)

[ref4] Seo S., Sharma V.K. and Sharma N., Mushroom Tyrosinase: Recent Prospects, J. Agric. Food Chem., 51, 2837-2853 (2007)

[ref5] Alijanianzadeh M., Saboury A.A., Mansouri-Torshizi H., Haghbeen K. and Moosavi-Movahedi A.A., The inhibitory effect of some new synthesized xanthates on mushroom tyrosinase, J.Enzym Inhib. Med. Chem., 22(2), 239-246 (2007)

[ref6] Rezaei Behbehani G., Divsalar A., Saboury A.A. and Gheibi N., A new approach for Thermodynamic Study on binding some metal ions with human growth hormone, J. Solution Chem., 37(12), 1645-1655 (2008)

[ref7] Rezaei Behbehani G., Divsalar A., Saboury A.A. and Bagheri M.J., A Thermodynamic Study on the Binding of human Serum Albumin with New synthesized Anti cancer Pd (II) complex, J. Solution Chem., 37(12), 1785-1794 (2008)

[ref8] Rezaei Behbehani G., Saboury A.A., Barzegar L., Zarean O., Abedini J. and Payehghdr M., A thermodynamic study on the interaction of nickel with myelin basic protein by isothermal titration calorimetry, J. Therm. Anal. Cal., 101(1), 379-384 (2010)

[ref9] Rezaei Behbehani G. and Mirzaie M., A high performance method for Thermodynamic Study on the Binding of Copper Ion and Glycine with Alzheimer's amyliod peptide, J. Therm. Anal. Cal., 96(2), 631-635 (2009)

[ref10] Saboury A.A., Atri M.S., Sanati M.H. and Sadeghi M., Application of a simple calorimetric data analysis on the binding study of calcium ions by human growth hormone, J. Therm. Anal. Cal., 83(1)175-179 (2006)