   1.17.3.2 | Cu2+ |
Cu2+ either stimulates or inhibits xanthine oxidase activity, depending on metal concentration (inhibition above 0.7 mM) and pre-incubation length, the latter also determining the inhibition type. Cu2+-enzyme complex formation is characterized by modifications in xanthine oxidase electronic absorption bands, intrinsic fluorescence, and alpha-helical and beta-sheet content. Apparent dissociation constant values imply high- and low-affinity Cu2+ binding sites in the vicinity of the enzyme's reactive centers, Cu2+ binding to high-affinity sites causes alterations around xanthine oxidase molybdenum and flavin adenine dinucleotide centers, changes in secondary structure, and moderate activity inhibition, binding to low affinity sites causes alterations around all xanthine oxidase reactive centers including FeS, changes in tertiary structure as reflected by alterations in spectral properties, and drastic activity inhibition. Stimulation is attributed to transient stabilization of xanthine oxidase optimal conformation. Potential role of copper in the regulation of xanthine oxidase activity, binding kinetics, detailed overview |
701447 |
