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1、ToxicologyinVitro21(2007)408–416www.elsevier.com/locate/toxinvitEVectofmercury,cadmium,nickel,chromiumandzinconkineticpropertiesofNADPH-cytochromeP450reductasepuriWedfromleapingmullet(Lizasaliens)a,¤bAzraBozcaarmutlu,EmelArinçaDepartmentofChemistry,InstituteofNaturalandAppliedScien
2、ces,AbantIzzetBaysalUniversity,14280Bolu,TurkeybBiochemistryGraduateProgrammeandDepartmentofBiologicalSciences,MiddleEastTechnicalUniversity,Ankara,TurkeyReceived17April2006;accepted4October2006Availableonline10October2006AbstractInformationonthemechanismofmetalioninhibitionofNADPH-
3、cytochromeP450reductaseislimited.ThepurposeofthepresentpaperwastoelucidateinvitroeVectofHg+2,Cd+2,Ni+2,Cr+3andZn+2ionsonthepuriWedmulletNADPH-cytochromeP450reductase.NADPH-cytochromeP450reductasewaspuriWedfromdetergent-solubilizedlivermicrosomesfromleapingmullet(Lizasaliens).Allofth
4、emetalionscausedinhibitionoftheenzymeactivityexceptZn+2.At50Mmetalconcentration,Hg+2inhibitedthecytochromeP450reductaseactivitycompletely(100%),while,atthesameconcentrations,Cd+2,Cr+3andNi+2caused66%,65%and37%inhibition,respec-tively.At50Mmetalconcentration,Zn+2hadnoapparenteVecto
5、ncytochromeP450reductaseactivity.TheICvaluesofHgCl,502CrCl,CdClandNiClwereestimatedtobe0.07M,24M,33Mand143M,respectively.Ofthemetalionstested,Hg+2exhibited322muchhigherinhibitoryeVectatlowerconcentrations,soitwasevidentlyamorepotentinhibitorthantheothers.Allfourmetalionsdis-play
6、ednoncompetitivetypeofinhibitionmechanismforthepuriWedreductaseasanalyzedbyDixonplot.KvaluesofHg+2,Cr+3,Cd+2,iandNi+2werecalculatedfromDixonplotsas0.048M,18M,73Mand329M,respectively.©2006ElsevierLtd.Allrightsreserved.Keywords:Noncompetitiveinhibition;Leapingmullet(Lizasaliens);N
7、ADPH-cytochromeP450reductase;Mercury;Cadmium;Nickel;Chromium;Zinc1.Introductiongenasesystem.ThemonoxygenasesystemconsistsofNADPH-cytochromeP450reductaseandafamilyofhemeNADPH-CytochromeP450reductase(NADPH:ferri-proteins,cytochromeP450,andisinvolvedinoxidativehemoproteinoxidoreductase
8、,EC1.6.2.4)isaninte
