A catalytic mechanism for benzylamine oxidase from pig plasma. Stopped-flow kinetic studies

1. Ammonium ion is shown to decrease the rate constants for Schiff's base formation and formation of a reduced intermediate during the catalytic cycle of benzylamine oxidase from pig plasma. The rat constant for reoxidation of the reduced intermediate is also inhibited whilst the rate constant for conversion of the oxidised enzyme form back to native enzyme is stimulated by ammonium ion. 2. Ammonium ion changes the electron paramagnetic resonance spectrum of the cupric centres in the enzyme, indicating that ammonia binds to the copper. 3. A catalytic mechanism for benzylamine oxidase is proposed on the basis of these and other results. This mechanism includes a novel step in which a hydroxyl coordinated to copper acts as a nucleophyle to facilitate hydride ion transfer to oxygen during the reoxidation process.