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Contribution of human manganese superoxide dismutase tyrosine 34 to structure and catalysis

Publication Type : Journal Article

Publisher : Biochemistry

Source : Biochemistry, Volume 48, Number 15, p.3417-3424 (2009)

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Keywords : Amines, amino acid analysis, amino acid substitution, Amino acids, animal cell culture, article, catalysis, Catalysts, Catalytic Domain, Catalytic intermediates, Catalytic rates, Catalytic roles, chemical mutagenesis, comparative study, Conserved Sequence, controlled study, crystal structure, crystallography, dissociation, DNA Mutational Analysis, enzyme activation, enzyme active site, enzyme inhibition, enzyme structure, Enzymes, human, Humans, Hydrogen, hydrogen bond, Hydrogen-bonded networks, kinetics, Manganese, manganese superoxide dismutase, molecular mechanics, Mutant enzymes, mutant protein, Neurodegenerative disease, Organic acids, Oxidation-Reduction, Oxygen, Plants (botany), priority journal, Product inhibitions, protein assembly, protein function, Protein Structure, Protein structures, Rate constants, Reactive Oxygen Species, reduction kinetics, structure activity relation, Structure-Activity Relationship, Structure-function studies, superoxide, superoxide dismutase, Superoxides, tyrosine, X-Ray

Year : 2009

Abstract : Superoxide dismutase (SOD) enzymes are critical in controlling levels of reactive oxygen species (ROS) that are linked to aging, cancer, and neurodegenerative disease. Superoxide (O 2 -) produced during respiration is removed by the product of the SOD2 gene, the homotetrameric manganese superoxide dismutase (MnSOD). Here, we examine the structural and catalytic roles of the highly conserved active-site residue Tyr34, based upon structure-function studies of MnSOD enzymes with mutations at this site. Substitution of Tyr34 with five different amino acids retained the active-site protein structure and assembly but caused a substantial decrease in the catalytic rate constant for the reduction of superoxide. The rate constant for formation of the product inhibition complex also decreases but to a much lesser extent, resulting in a net increase in the level of product inhibited form of the mutant enzymes. Comparisons of crystal structures and catalytic rates also suggest that one mutation, Y34V, interrupts the hydrogen-bonded network, which is associated with a rapid dissociation of the product-inhibited complex. Notably, with three of the Tyr34 mutants, we also observe an intermediate in catalysis, which has not been reported previously. Thus, these mutants establish a means of trapping a catalytic intermediate that promises to help elucidate the mechanism of catalysis. © 2009 American Chemical Society.

Cite this Research Publication : J. J. Pab Perry, Hearn, A. Sc, Cabelli, D. Ed, Nick, H. Sc, Tainer, J. Aae, and Silverman, D. Nf, “Contribution of human manganese superoxide dismutase tyrosine 34 to structure and catalysis”, Biochemistry, vol. 48, pp. 3417-3424, 2009.

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