Abstract: BACKGROUND AND AIM: To purify and investigate the enzyme kinetic properties of rabbit plasma semicarbazide_sensitive amine oxidases(SSAO), using methylamine as substrate. MATERIALS AND METHODS: Formaldehyde, an oxidative deamination product of methylamine, was analyzed by HPLC. Rabbit plasma SSAO was purified by chromatography with DEAE_sepharose FF(eluted with 30 mmol/L and then 100 mmol/L sodium phosphate buffers, all at pH 7.0), then assayed and Michaelis_Menten analyzed. RESULTS: Two fractions of plasma (labeled as peak A and peak B) obtained were catalytically active with methylamine as substrate. The kinetic parameters Km and Vmax of plasma were(1.83±0.13) mmol/L and(0.12±0.003)nmol/(min·mg), respectively. The Km of peak B (2.05±0.43)mmol/L was lower than that of peak A (3.14±0.63)mmol/L, the Vmax of the peak B (1.46±0.10) nmol/(min·mg) was lower than that of peak A (2.85±0.20) nmol/(min·mg). CONCLUSION: In rabbit plasma, there were two kinds of SSAO, which could catalyze the oxidative deamination of methylamine into formaldehyde, had significantly different kinetic parameters.

Key words: semicarbazide_sensitive amine oxidase, methylamine, Michaelis_Menten analysis