Biophys J, October 2002, p. 2231-2239, Vol. 83, No. 4

Binding of Cations of Group IA and IIA to Bovine Serum Amine Oxidase: Effect on the Activity

Maria Luisa Di Paolo,^* Marina Scarpa, Alessandra Corazza, Roberto Stevanato,^§ and Adelio Rigo^*

 ^*Dipartimento di Chimica Biologica, Università di Padova, 35121 Padova;  Dipartimento di Fisica and INFM, Università di Trento, 38050 Povo-Trento;  Dipartimento di Scienze e Tecnologie Biomediche, Università di Udine, 33100 Udine; and  ^§Dipartimento di Chimica Fisica, Università di Venezia, 30100 Venezia, Italy

In this paper, we report on the presence of cation binding areas on bovine serum amine oxidase, where metal ions of the groups IA and IIA, such as Na⁺, K⁺, Cs⁺, Mg²⁺, and Ca²⁺, bind with various affinities. We found a cation-binding area that influences the enzyme activity if occupied, so that the catalytic reaction may be altered by some physiologically relevant cations, such as Ca²⁺ and K⁺. This binding area appears to be localized inside the enzyme active site, because some of these cations act as competitive inhibitors when highly charged amines, such as spermine and spermidine, are used as substrates. In particular, dissociation constant values (K_d) of 23 and 27 mM were measured for Cs⁺ and Ca²⁺, respectively, using, as substrate, spermine, a polyamine of plasma. An additional cation-binding area, where metal ions such as Cs⁺ (K_d  0.1 mM) and Na⁺ (K_d  54 mM) bind without affecting the enzyme activity, was found by NMR.

Biophys J, October 2002, p. 2231-2239, Vol. 83, No. 4
© 2002 by the Biophysical Society   0006-3495/02/10/2231/09  $2.00