| The following arsenite methyltransferase activities (U/mg) were measured in untreated mice: liver, 1.42 ± 0.17 (mean ± SEM); kidney, 0.62 ± 0.18; lung, 0.33 ± 0.08; testis, 1.21 ± 0.01. Arsenite methyltransferase metabolites were not detectable using guinea pig liver, kidney, lung or testis cytosol as the source of enzyme. A twofold increase in liver arsenite methyltransferase activity was observed in mice exposed to 28.6 mg sodium arsenite/L drinking water after 24 hr compared to control.; Trivalent arsenic species were separated from pentavalent arsenicals in liver homogenates of hamsters injected 15 hr priorly with [73As]arsenate by (CCl4)-20 mM (DDDC) extraction and both phases analyzed by HPLC. Metabolites of inorganic arsenate were observed in the following concentrations (ng/g liver ± SEM); MMAIII, 38.5 ± 2.9; DMA III, 49.9 ± 10.2; arsenite, 35.5 ± 3.0; arsenate, 118.2 ± 8.7; MMAv, 31.4 ± 2.8; and DMAv, 83.5 ± 6.7.; Neither in vitro nor in vivo arsenite methyltransferase activity could be detected in S. cerevisiae . Attempting to induce enzyme activity, yeast were grown in 0–100 mM, 8 μCi [73As]Na2HAsO4. No methylated metabolites were detected in cell lysate or media under these experimental conditions.; The dissociation constants for guinea pig and rabbit cytosolic arsenite binding proteins were determined to be 59.62 ± 11.97 and 120.4 μM AsIII, respectively, and the respective specificities, 53.83 ± 3.67% and 59%. Guinea pig arsenite binding protein was fractionated using bioaffinity and size exclusion chromatography to yield partially purified protein(s) with an approximate molecular weight of 115 kDa.; Arsenite methyltransferase activity was purified >7000-fold from rabbit liver and identified as 1 cys peroxiredoxin, a conserved family of antioxidant proteins characterized by non-selenium dependent glutathione peroxidase and calcium-independent phospholipase A2 activities. Murine 1 cys peroxiredoxin was cloned and expressed in E. coli and S. cerevisiae and expressed in reticulocyte lysate. Recombinant proteins had neither arsenite methyltransferase nor glutathione peroxidase activities. Antibodies directed against 1-cys peroxiredoxin immunoprecipitated a ∼29 kDa protein from guinea pig kidney cytosol which was identified as 1-cys peroxiredoxin by LC-MS/MS. Under these experimental conditions, guinea pig kidney cytosol did not catalyze the reduction of peroxides... |
