title: Effect of Mn2+, Co2+, Ni2+, and Cu2+ on horseradish peroxidase: activation, inhibition, and denaturation studies.
abstract: The effects of transition metal ions (M2+) such as Mn2+, Co2+, Ni2+, and Cu2+ on the functional and structural stabilities of horseradish peroxidase (HRP) were investigated with respect to reversible chemical denaturation, Michaelis-Menten kinetics, chemical modification and time-dependent catalytic activity. Conformational Gibbs free energy (deltaGo(H2O)) as a structural stability criterion and transition concentrations of metal ions ([M2+] 1/2) were estimated using a two-state chemical denaturation model. Activation and inhibitory concentration ranges for each metal ion were specified by the steady-state enzyme kinetics. Results of a pH-profile method confirmed by chemical modification indicate that a histidine residue interacts in the activation concentration range, whereas carboxylic residues (Asp and Glu) contribute to interaction in the inhibitory concentration range. Incubation of the enzyme with the metal ion at activation concentration leads to long-term functional stability of peroxidase. Thus, such metal ions as potent effectors induced the enhancement of conformational and functional stabilities of horseradish peroxidase.
authors.affiliation: Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran.
authors.forename: A
authors.initials: A
authors.lastname: Mahmoudi
authors.forename: K
authors.initials: K
authors.lastname: Nazari
authors.forename: N
authors.initials: N
authors.lastname: Mohammadian
authors.forename: A A
authors.initials: AA
authors.lastname: Moosavi-Movahedi
mesh_terms: D003035:Cobalt / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000737:chemistry; D004795:Enzyme Stability; D006139:Guaiacol / Q000737:chemistry*; D006735:Horseradish Peroxidase / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000737:chemistry; D008956:Models, Chemical; D009532:Nickel / Q000737:chemistry; D011489:Protein Denaturation; D012680:Sensitivity and Specificity; D013329:Structure-Activity Relationship; D028561:Transition Elements / Q000737:chemistry*
chemical_list: D004791:Enzyme Inhibitors; D028561:Transition Elements; D003035:Cobalt; D006139:Guaiacol; D003300:Copper; D009532:Nickel; D006735:Horseradish Peroxidase; D008274:Magnesium