title: Interaction of Cu2+ ion with milk xanthine oxidase.
abstract: The interaction of Cu2+ ion with milk xanthine oxidase (XO) has been studied by optical spectroscopy, circular dichroism, ESR and transient kinetic techniques. It is observed that XO forms optically observable complexes with Cu2+ ion. The pH dependence studies of the formation of Cu2+-XO complex by optical spectroscopy and circular dichroism show that at least one ionizable group may be responsible for the formation of the complex. The EPR studies show that Cu2+ ion binds to XO with sulfur and nitrogenous ligands. The transient kinetic study of the interaction of Cu2+ with XO shows the existence of two Cu2+ bound XO complexes formed at two different time scales of the interaction, one at < or =5 ms and the other one at around 20 s. The complex formed at longer time scale may be responsible for the inhibition of the enzyme activity.
authors.affiliation: Department of Chemical Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, 40 0005, Mumbai, India. apurba@mail.utexas.edu
authors.forename: A K
authors.initials: AK
authors.lastname: Sau
authors.forename: M S
authors.initials: MS
authors.lastname: Mondal
authors.forename: S
authors.initials: S
authors.lastname: Mitra
mesh_terms: D000818:Animals; D002942:Circular Dichroism; D003300:Copper / Q000378:metabolism*; D004578:Electron Spin Resonance Spectroscopy; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008892:Milk / Q000201:enzymology*; D011485:Protein Binding; D013696:Temperature; D014969:Xanthine Oxidase / Q000378:metabolism*
chemical_list: D003300:Copper; D014969:Xanthine Oxidase