Methylamine dehydrogenase of Pseudomonas AM1. A subunit enzyme.

A methylamine dehydrogenase was purified to homogeneity from Pseudomonas AM1 and obtained in crystalline form. It was found to be a subunit enzyme composed of two kinds of subunit, light and heavy. These two subunits were isolated by Sephadex G-100 gel chromatography after incubation of the enzyme with guanidine hydrochloride. Molecular weights of 13,000 daltons for the light subunit and 40,000 daltons for the heavy subunit were estimated by SDS-polyacrylamide gel electrophoresis, and the molecular weight of the native enzyme was found to be 105,000 daltons by Sephadex G-200 gel chromatography. The enzyme and its subunits were also analyzed for amino acid composition, isoelectric point, and absorption fluorescence, and CD spectra, as well as for the effects of pH, thermal treatment, and guanidine hydrochloride treatment. Both the subunits were absolutely required for enzymatic activity, either subunit alone being inactive. It could be deduced from the absorption and fluorescence spectra of the subunits that the prosthetic group of the enzyme was bound solely to the light subunit. These results suggest that the enzyme is a subunit enzyme similar to that of Pseudomonas sp. J, of the alpha2beta2 type.