Effect of mercury, cadmium, nickel, chromium and zinc on kinetic properties of NADPH-cytochrome P450 reductase purified from leaping mullet (Liza saliens)


Bozcaarmutlu A., Arinc E.

TOXICOLOGY IN VITRO, vol.21, no.3, pp.408-416, 2007 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 21 Issue: 3
  • Publication Date: 2007
  • Doi Number: 10.1016/j.tiv.2006.10.002
  • Title of Journal : TOXICOLOGY IN VITRO
  • Page Numbers: pp.408-416
  • Keywords: noncompetitive inhibition, leaping mullet (Liza saliens), NADPH-cytochrome p450 reductase, mercury, cadmium, nickel, chromium, zinc, NADPH-CYTOCHROME-P-450 REDUCTASES, INHIBITION-KINETICS, LIVER MICROSOMES, P-450 REDUCTASE, METAL-IONS, PIG-LIVER, SYSTEM, OXIDOREDUCTASE, PURIFICATION, RELEVANCE

Abstract

Information on the mechanism of metal ion inhibition of NADPH-cytochrome P450 reductase is limited. The purpose of the present paper was to elucidate in vitro effect of Hg(+2), Cd(+2), Ni(+2), Cr(+3) and Zn(+2) ions on the purified mullet NADPH-cytochrome P450 reductase. NADPH-cytochrome P450 reductase was purified from detergent-solubilized liver microsomes from leaping mullet (Liza saliens). All of the metal ions caused inhibition of the enzyme activity except Zn(+2). At 50 mu M metal concentration, Hg(+2) inhibited the cytochrome P450 reductase activity completely (100%), while, at the same concentrations, Cd(+2), Cr(+3) and Ni(+2) caused 66%, 65% and 37% inhibition, respectively. At 50 mu M metal concentration, Zn(+2) had no apparent effect on cytochrome P450 reductase activity. The IC(50) values of HgCl(2), CrCl(3), CdCl(2) and NiCl(2) were estimated to be 0.07 mu M, 24 mu M, 33 mu M and 143 mu M, respectively. Of the metal ions tested, Hg(+2) exhibited much higher inhibitory effect at lower concentrations, so it was evidently a more potent inhibitor than the others. All four metal ions displayed noncompetitive type of inhibition mechanism for the purified reductase as analyzed by Dixon plot. K(i) values of Hg(+2), Cr(+3), Cd(+2) and Ni(+2) were calculated from Dixon plots as 0.048 mu M, 18 mu M, 73 mu M and 329 mu M, respectively. (c) 2006 Elsevier Ltd. All rights reserved.