ABSTRACT
Because the prosthetic group was covalently attached, extensive proteolytic treatment and subsequent chromatography under denaturing conditions were required to isolate relatively small prosthetic group-containing peptides, which were used in subsequent analyses of structure. A Hammett plot of the rate constant for reduction of the enzyme-benzylamine complex against substituent constants exhibited a positive slope, which suggested that the oxidation of these amines by methylamine dehydrogenase proceeds through a carba-nionic reaction intermediate. The reduction and inhibition by benzylamines of methylamine dehydrogenase is particularly interesting given similar results that have been observed with eukaryotic quinoprotein amine oxidases. Many studies have been performed on interactions of methylamine dehydrogenases with other isolated periplasmic redox proteins from their host bacteria. The specificity of the interaction between amicyanin and methylamine dehydrogenase is best demonstrated by studies of the isolated proteins from P. denitrificans. Without such data it is not possible to assign a reaction mechanism for the oxidative half-reaction of this enzyme with its physiological electron acceptor.
