EFFECT OF POLYPHOSPHATES ON THE ACTIVITY OF AMINE OXIDASES

The interaction between polyphosphates and polyamines was investigated by P-31-NMR spectroscopy and by amine oxidase activity measurements. An apparent competition between negatively charged polyphosphates (ATP , ADP, AMP, tripolyphosphate and pyrophosphate) and positively charged polyamine, for the active site of bovine serum and soybean seedling a mine oxidases, was observed by activity measurements. This behavior wa s explained by formation of polyamine-polyphosphate complexes and the stability constants of these complexes were calculated by P-31 NMR. Ho wever, at a given concentration of polyphosphate, the amine oxidase ac tivity was found higher than that expected on the basis of the free am ine concentration calculated according to the NMR stability constant, This fact, and the different extent of inhibition of the spermidine ox idase activity of soybean seedling and of bovine serum amine oxidases observed in the presence of a given polyphosphate, suggest that amine oxidases may be active also on the polyamine-polyphosphate complexes. This hypothesis was supported by the strong dependence of the k(cat)/K -m of bovine serum amine oxidase on ionic strength, indicating an elec trostatic interaction between the charged amine and the active site, w hile no effect of ionic strength on k(cat)/K-m was observed in the pre sence of ATP. A kinetic model of this behavior was found to fit the ex perimental data.