Metallic mercury-releasing enzyme (MMR-Enz) which catalyzes the reduction of mercury in organic and inorganic mercurials to metallic mercury was purified about 90-fold from the cell-free extract of mercury-resistant Pseudomonas by means of ammonium sulfate precipitation and repeat of column chromatography on Sephadex G-150 and on DEAE-Sephadex. The purified enzyme showed a single band in electrophoresis on polyacrylamide gel, and also _??_ characteristic absorption spectrum indicative of flavoprotein. A prosthetic group of the enzyme was identified as FAD by thin-layer chromatography. The identification was confirmed by the reconstitution of active D-amino acid oxidase from the apoenzyme, and by the reactivation of ultraviolet light-irradiated MMR-Enz with FAD. Organic mercurials (phenyl, methyl and ethyl mercurials) and inorganic mercurials were reductively decomposed forming metallic mercury by the action of the purified MMR-Enz in the presence of reduced NAD (P) generating system and cytochrome c-I.
Japan Society for Bioscience, Biotechnology, and Agrochemistry