Copper/Topaquinone-Containing Amine Oxidase from Lentil Seedlings and Bovine Plasma: Catalytic Mechanism and Energetic Domains

�R. Medda^a, S. Longu^a, E. Agostinelli^b, L. Dalla Vedova^b, J.Z. Pedersen^c, G. Floris^a, A.A. Moosavi-Movahedi^d and A. Padiglia^a,*
^a Department of Applied Sciences in Biosystems, University of Cagliari, Cagliari, Italy
^b Department of Biochemical Sciences, University of Rome "La Sapienza�, and CNR Biology and Molecular Pathology Institutes, Piazzale A. Moro 5, 00185 Rome, Italy
^c Department of Biology, University of Rome �Tor Vergata�, Rome, Italy
^d Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran

�(Received 27 December 2003,� Accepted 6 March 2004)

������ In this review the characteristics of the prosthetic group and the role of copper in amine oxidase purified from lentil seedlings are compared with the corresponding features of the amine oxidase isolated from bovine serum. Although both enzymes contain the same organic cofactor, the 6-hydroxydopa (2,4,5-trihydroxyphenethylamine) quinone, the catalytic cycle of lentil seedling amine oxidase operates through a Cu(I)-free-radical intermediate of the cofactor, whereas in bovine serum enzyme the radical form was not observed. The role of the metal in the catalytic mechanism of the two enzymes is also discussed. Moreover, the energetic domains and the effect of the temperature on activity, for both enzymes, are examined using differential scanning calorimetry.

Keywords: Amine oxidase, Copper, 6�Hydroxydopa, Differential scanning calorimetry, Deconvolution