eng Science and Education Publishing American Journal of Medical and Biological Research 2328-4099 2016-08-06 4 3 42 52 10.12691/ajmbr-4-3-2 AJMBR2016432 article Usenobong F. Ufot usen_mboso@yahoo.com 1 Aniefiok E. Ite 2 3 Idorenyin H. Usoh 3 Monday I. Akpanabiatu 4 Department of Biological Sciences, Akwa Ibom State University, P.M.B. 1167, Uyo, Akwa Ibom State, Nigeria Department of Chemistry, Akwa Ibom State University, P.M.B. 1167, Uyo, Akwa Ibom State, Nigeria Department of Biochemistry, University of Uyo, P. M. B. 1017, Uyo, Akwa Ibom State, Nigeria This study investigated the steady-state kinetics of engineered wild-type and manganese (II) binding site mutants of recombinant Phlebia radiata manganese peroxidase 3(rPr-MnP3). The effect (activation or inhibition) of some metal ions (Co2+, Zn2+ Cu2+ and Na+) on the activity of rPr-MnP3 enzymes was also studied. The results obtained showed that the rPr-MnP3 mutants in which the metal binding functionality has been largely lost have been created. Na+ (mono-valent ion) and Co2+showed similar characteristics by exhibiting stimulatory effects on the activity of wild-type rPr-MnP3. However, Cu2+ and Zn2+ had mixed inhibitory effects on wild-type and mutants (E40H, E44H, E40H/E44H). It was observed that Cu2+ was by far the strongest inhibitor of engineered rPr-MnP3 enzymes while Co2+ exhibited a non-competitive inhibitory effect on the double mutant (E40H/E44H) and D186H activities. In addition, Zn2+ and Cu2+also had non-competitive inhibitory effect on D186H mutant enzyme activity. The results obtained further showed that the competitive inhibitory effect of Cu2+observed in other rPr-MnP3 enzymes is largely removed in D186H mutant enzyme. Generally, histidine substitution retained a strong selectivity for Cu2+ as competitive inhibitor. Zn2+ being generally non-competitive suggest involvement of sites other than the Mn (II) binding site. This study showed that rPr-MnP3 enzymes function with alternate ligands in the Mn2+ binding site and does not have absolute obligate requirement for all carboxylate ligand set. http://pubs.sciepub.com/ajmbr/4/3/2/ajmbr-4-3-2.pdf peroxidase Phlebiaradiata steady-state wild-type mutants metal ions inhibitors