Cytotoxicity and Kinetic Analysis of Purified Bovine Serum Amine Oxidase in the Presence of Spermine in Chinese Hamster Ovary Cells

Bovine serum amine oxidase (BSAO, EC 1.4.3.6) catalyzes the oxidative deamination of polyamines giving rise to the corresponding aldehydes, ammonia and hydrogen peroxide (H2O2). This study demonstrates that amine oxidase (BSAO) purified from bovine serum and exogenous spermine caused cytotoxicity in Chinese hamster ovary (CHO) cells. Cytotoxicity occurred when cells were exposed to BSAO (0.0164-16.4 μg/ml) in the presence of spermine (1.9-340 μM). BSAO and spermine alone were not toxic at these concentrations. Cytotoxicity was dependent on the concentration of spermine and on the incubation time, and was also accelerated at 42°C relative to 37°C. Kinetic analysis of the enzymatic reaction, as a function of spermine concentration, showed Michaelis-Menten saturation kinetics. The apparent Vmax increased from 19.1 ± 0.4 μM min−1 at 37°C to 23.0 ± 0.3 μM min−1 at 42°C. The apparent Km decreased from 25.5 ± 2.6 μM at 37°C to 17.7 ± 1.3 μM at 42°C. Catalase inhibited cytotoxicity, suggesting that H2O2 was partially responsible for cytotoxicity. This work shows that the oxidation products of polyamines, rather than the polyamines themselves, are responsible for cytotoxicity in mammalian cells. The significance of this study is that amine oxidases could have therapeutic potential in cancer treatment regimens and a beneficial effect is likely when the enzyme is used together with clinical hyperthermia.