Oxidation of benzylamine Br-derivatives by lentil seedling copper-amine oxidase

Copper amine oxidase was shown to be able to catalyse the oxidative deamination of 2-, 3- and 4-Br-derivatives of benzylamine to the corresponding aldehydes, that all absorb at 250 nm. This change in the absorption spectrum made it possible to follow the enzyme reaction. 2-Br-benzylamine, 3-Br-benzylamine, and 4-Br-benzylamine showed Km values similar to benzylamine, but 3-Br-benzylamine showed a slower kc, which allows it to be a catalytically more efficient substrate. Under anaerobic conditions the native enzyme oxidised 1 equivalent of all Br-derivatives and released 1 equivalent of aldehyde per enzyme subunit. These findings demonstrate that, in anaerobic conditions, the enzyme can oxidise substrates with a single incomplete turnover. The possible involvement of the cofactor 6-hydroxydopa quinone and of a negatively charged residue in the oxidation of Br-benzylamines is discussed.