Cysteamine Oxygenase: Possible Involvement of Superoxide Ion in the Catalytic Mechanism

G. Ricci Institutes of Biological Chemistry, Universities of Ronie “La Sapienza” and Chieti; Department of Cell Biology and Physiology, University of L'Aquila; CNR Centre for Molecular Biology, Rome; Department of Biology, University of Rome, Tor Vergata, Italy

S. Duprè Institutes of Biological Chemistry, Universities of Ronie “La Sapienza” and Chieti; Department of Cell Biology and Physiology, University of L'Aquila; CNR Centre for Molecular Biology, Rome; Department of Biology, University of Rome, Tor Vergata, Italy

G. Federici Institutes of Biological Chemistry, Universities of Ronie “La Sapienza” and Chieti

M. Nardini Institutes of Biological Chemistry, Universities of Ronie “La Sapienza” and Chieti; Department of Cell Biology and Physiology, University of L'Aquila; CNR Centre for Molecular Biology, Rome; Department of Biology, University of Rome, Tor Vergata, Italy

G. Spoto Institutes of Biological Chemistry, Universities of Ronie “La Sapienza” and Chieti; Department of Cell Biology and Physiology, University of L'Aquila; CNR Centre for Molecular Biology, Rome; Department of Biology, University of Rome, Tor Vergata, Italy

D. Cavallini Institutes of Biological Chemistry, Universities of Ronie “La Sapienza” and Chieti; Department of Cell Biology and Physiology, University of L'Aquila; CNR Centre for Molecular Biology, Rome; Department of Biology, University of Rome, Tor Vergata, Italy

Abstract

The reaction catalyzed by cysteamine oxygenase on cysteamine in the presence of phenazine methosulphate as cofactor like compound is inhibited by nitroblue tetrazolium, a scavenger of superoxide ions. The reaction is not inhibited by superoxide dismutase and allyl alcohol and it is not activated by superoxide ions produced in solution. Nitroblue tetrazolium is reduced by cysteamine or mercaptoethanol and phenazine methosulphate. This reaction is completely inhibited by superoxide dismutase. In the presence of cysteamine oxygenase the reduction with mercaptoethanol is greatly enhanced and it is only partially inhibited by superoxide dismutase. According to these data a reaction mechanism is proposed in which superoxide ions and thiyl radicals are produced at the active site during catalysis.

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Cysteamine Oxygenase: Possible Involvement of Superoxide Ion in the Catalytic Mechanism

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Cysteamine Oxygenase: Possible Involvement of Superoxide Ion in the Catalytic Mechanism

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