title: Cell-free mercury(II)-reducing activity in a plasmid-bearing strain of Escherichia coli.
abstract: The ability to reduce Hg(II) to Hg(0), which is determined by a plasmid-borne gene in Escherichia coli, is conferred by a Hg(II)-inducible activity which is located in the cytoplasm rather than in the periplasmic space of the cell. This Hg(II)-reducing activity can be isolated from the supernatant of a 160,000 x g centrifugation after French Press disruption of the cells. The activity is dependent on glucose-6-phosphate, glucose-6-phosphate dehydrogenase, and 2-mercaptoethanol, but is not enhanced by added nicotinamide adenine dinucleotide phosphate. Treatment of the active fraction with N-ethylmaleimide causes irreversible loss of the Hg(II)-reducing activity. Unlike the Hg(II)-reducing activity found in intact cells, the cell-free activity is not inhibited by toluene, potassium cyanide, or m-chlorocarbonylcyanide-phenylhydrazone; however, it is inhibited by Ag(I) and phenylmercuric acetate to the same extent as the activity in intact cells. Neither phenylmercuric acetate nor methylmercuric chloride is reduced to Hg(0) by the cell-free activity. Au(III), however, is a substrate for the cell-free activity; it is reduced to metallic colloidal Au(0).
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D002473:Cell Wall / Q000201:enzymology; D002474:Cell-Free System; D003593:Cytoplasm / Q000201:enzymology; D003956:Dialysis; D004352:Drug Resistance, Microbial; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D005033:Ethylmaleimide / Q000494:pharmacology; D005111:Extrachromosomal Inheritance; D005696:Galactosidases / Q000378:metabolism; D005796:Genes; D006046:Gold / Q000378:metabolism; D008623:Mercaptoethanol / Q000494:pharmacology; D008628:Mercury / Q000378:metabolism* / Q000494:pharmacology; D008629:Mercury Isotopes; D009942:Organometallic Compounds / Q000378:metabolism; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000302:isolation & purification / Q000378:metabolism*; D011868:Radioisotopes; D012834:Silver / Q000378:metabolism; D013104:Spheroplasts / Q000201:enzymology
chemical_list: D008629:Mercury Isotopes; D009942:Organometallic Compounds; D011868:Radioisotopes; D012834:Silver; D008623:Mercaptoethanol; D006046:Gold; D010088:Oxidoreductases; D000469:Alkaline Phosphatase; D005696:Galactosidases; D008628:Mercury; D005033:Ethylmaleimide