75-60-5Relevant articles and documents
The rate of oxidation of dimethylarsinous acid to dimethylarsinic acid is pH dependent: Implications for the analysis and toxicology of arsenic metabolites in urine
Nakayama, Takashi,Edmonds, John S.,Shibata, Yasuyuki,Morita, Masatoshi
, p. 185 - 187 (2006)
A 1H NMR spectroscopic study has shown the rate oxidation of dimethylarsinous acid to dimethylarsinic acid in buffered aqueous solutions to depend upon pH. Dimethylarsinous acid has been reported to be a highly toxic arsenical metabolite and component of the urine of persons exposed to inorganic arsenic, particularly through drinking water. As the pH of human urine can range from 4.5 to 8, the pH dependence of the oxidation rate of dimethylarsinous acid to dimethylarsinic acid has profound implications for the detection and analysis of these compounds in urine samples, and for the relevance of the experimental toxicology of dimethylarsinous acid.
Methylated Phenylarsenical Metabolites Discovered in Chicken Liver
Peng, Hanyong,Hu, Bin,Liu, Qingqing,Li, Jinhua,Li, Xing-Fang,Zhang, Hongquan,Le, X. Chris
supporting information, p. 6773 - 6777 (2017/06/06)
We report the discovery of three toxicologically relevant methylated phenylarsenical metabolites in the liver of chickens fed 3-nitro-4-hydroxyphenylarsonic acid (ROX), a feed additive in poultry production that is still in use in several countries. Methyl-3-nitro-4-hydroxyphenylarsonic acid (methyl-ROX), methyl-3-amino-4-hydroxyphenylarsonic acid (methyl-3-AHPAA), and methyl-3-acetamido-4-hydroxyphenylarsonic acid (or methyl-N-acetyl-ROX, methyl-N-AHPAA) were identified in such chicken livers, and the concentration of methyl-ROX was as high as 90 μg kg?1, even after a five-day clearance period. The formation of these newly discovered methylated metabolites from reactions involving trivalent phenylarsonous acid substrates, S-adenosylmethionine, and the arsenic (+3 oxidation state) methyltransferase enzyme As3MT suggests that these compounds are formed by addition of a methyl group to a trivalent phenylarsenical substrate in an enzymatic process. The IC50 values of the trivalent phenylarsenical compounds were 300–30 000 times lower than those of the pentavalent phenylarsenicals.
Enzymatic methylation of arsenic compounds: Assay, partial purification, and properties of arsenite methyltransferase and monomethylarsonic acid methyltransferase of rabbit liver
Zakharyan,Wu,Bogdan,Aposhian
, p. 1029 - 1038 (2007/10/03)
A rapid, accurate, in vitro assay utilizing radioactive S-adenosylmethionine (SAM) has been developed for the methylation of arsenite and monomethylarsonate (MMA) by rabbit liver methyltransferases. The assay has been validated by separating, identifying, and measuring the products of the reaction using chloroform extraction, ion exchange chromatography, TLC, or HPLC. The enzymes involved in this pathway, arsenite methyltransferase and MMA methyltransferase, have been purified approximately 2000-fold from rabbit liver. After gel electrophoresis, a single band is obtained with both enzyme activities in it. The pH optima for purified arsenite methyltransferase and monomethylarsonic acid methyltransferase are 8.2 and 8.0, respectively. A thiol, S-adenosylmethionine, and arsenite are required for the partially purified arsenite methyltransferase that catalyzes the synthesis of monomethylarsonate. A different enzyme activity that catalyzes the methylation of monomethylarsonate to dimethylarsinate also requires SAM and a thiol. Even though arsenite methyltransferase and monomethylarsonate methyltransferase have different substrates, pH optima, and saturation concentrations for their substrates, whether the two activities are present on one protein molecule or different protein molecules is still uncertain. Both activities have a molecular mass of 60 kDa as determined by gel exclusion chromatography. There is no evidence at the present time for these enzyme activities being on different protein molecules. Neither arsenate, selenate, selenite, or selenide are methylated by the purified enzyme preparations. Results from the use of crude extracts, often called cytosol, to study the properties of these methyltransferases dealing with arsenic species should be viewed with caution since such crude extracts contain inhibiting and other interfering activities.