Purification And Catalytic Properties Of Rabbit Plasma Semicarbazide-sensitive Amine Oxidases

BACKGROUND AND AIM: To purify and investigate 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 examined by HPLC analysis. Rabbit plasma SSAO was purified by chromatography with DEDE-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 kinds of SSAOs (labeled as peak A and peak B) had been obtained, which were catalytically active with methylamine as substrate. The kinetic parameters Km and Vmax of plasma were 1.83±0.13 mmol/L and 22.20±0.48 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 A (1.03±0.07 nmol/min/mg) was lower than that of peak B (2.52±0.17 nmol/min/mg). CONCLUSION: In rabbit plasma, there are two kinds of SSAO which can catalyze methylamine into formaldehyde and have significantly different kinetic parameters.