Abstract
The metabolism of arsenic is generally accepted to proceed by repetitive reduction and oxidative methylation; the latter is mediated by arsenic methyltransferase (Cyt19). In human urine, the major metabolites of inorganic arsenicals such as arsenite (iAsIII) and arsenate (iAsV) are monomethylarsonic acid (MMAV) and dimethylarsinic acid (DMAV). On the other hand, in rat bile, the major metabolites of iAsIII have been reported to be arsenic–glutathione (As-GSH) complexes. In the present study we investigate whether these As-GSH complexes are substrates for arsenic methyltransferase by using human recombinant Cyt19. Analyses by high-performance liquid chromatography–inductively coupled plasma mass spectrometry suggested that arsenic triglutathione (ATG) was generated nonenzymatically from iAsIII when GSH was present at concentrations 2 mM or higher. Human recombinant Cyt19 catalyzed transfer of a methyl group from S-adenosyl-l-methionine to arsenic and produced monomethyl and dimethyl arsenicals. The methylation of arsenic was catalyzed by Cyt19 only when ATG was present in the reaction mixture. Moreover, monomethylarsonic diglutathione (MADG) was a substrate of Cyt19 for further methylation to dimethylarsinic glutathione (DMAG). On the other hand, monomethylarsonous acid (MMAIII), a hydrolysis product of MADG, was not methylated to dimethyl arsenical by Cyt19. These results suggest that As-GSH complexes such as ATG and MADG were converted by Cyt19 to MADG and DMAG, respectively. Both MADG and DMAG were unstable in solution when the GSH concentration was lower than 1 mM, and were hydrolyzed and oxidized to MMAV and DMAV, respectively. Metabolism of iAsIII to methylated arsenicals by Cyt19 was via ATG and MADG rather than by oxidative methylation of iAsIII and MMAIII.
![](https://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs00204-004-0620-x/MediaObjects/s00204-004-0620-xflb1.gif)
![](https://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs00204-004-0620-x/MediaObjects/s00204-004-0620-xflb2.gif)
![](https://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs00204-004-0620-x/MediaObjects/s00204-004-0620-xflb3.gif)
![](https://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs00204-004-0620-x/MediaObjects/s00204-004-0620-xflb4.gif)
![](https://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs00204-004-0620-x/MediaObjects/s00204-004-0620-xflb5.gif)
![](https://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs00204-004-0620-x/MediaObjects/s00204-004-0620-xflb6.gif)
![](https://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs00204-004-0620-x/MediaObjects/s00204-004-0620-xflb7.gif)
![](https://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs00204-004-0620-x/MediaObjects/s00204-004-0620-xflb8.gif)
![](https://media.springernature.com/m312/springer-static/image/art%3A10.1007%2Fs00204-004-0620-x/MediaObjects/s00204-004-0620-xflb9.gif)
Similar content being viewed by others
Explore related subjects
Discover the latest articles, news and stories from top researchers in related subjects.References
Aposhian HV (1997) Enzymatic methylation of arsenic species and other new approaches to arsenic toxicity. Annu Rev Pharmacol Toxicol 37:397–419
Aposhian HV, Gurzau ES, Le XC, Gurzau A, Healy SM, Lu X, Ma M, L Yip, Zakharyan RA, Maiorino RM, Dart RC, Tircus MG, Gonzalez Ramirez D, Morgan DL, Avram D, Aposhian MM (2000) Occurrence of monomethylarsonous acid in urine of humans exposed to inorganic arsenic. Chem Res Toxicol 13:693–697
Aposhian HV, Zakharyan RA, Avram MD, Kopplin MJ, Wollenberg ML (2003) Oxidation and detoxification of trivalent arsenic species. Toxicol Appl Pharmacol 193:1–8
Buchet JP, Lauwerys R (1985) Study of inorganic arsenic methylation by rat-liver in vitro—relevance for the interpretation of observations in man. Arch Toxicol 57:125–129
Buchet JP, Lauwerys R (1987) Study of factors influencing the in vivo methylation of inorganic arsenic in rats. Toxicol Appl Pharmacol 91:65–74
Buchet JP, Lauwerys R (1988) Role of thiols in the in vitro methylation of inorganic arsenic by rat-liver cytosol. Biochem Pharmacol 37:3149–3153
Crecelius EA (1977) Changes in the chemical speciation of arsenic following ingestion by man. Environ Health Perspect 19:147–150
Engel RR, Smith AH (1994) Arsenic in drinking-water and mortality from vascular-disease—an ecologic analysis in 30 counties in the United States. Arch Environ Health 49:418–427
Hansen HR, Raab A, Jaspars M, Milne BF,Feldmann J (2004) Sulfur-containing arsenical mistaken for dimethylarsinous acid [DMA(III)] and identified as a natural metabolite in urine: major implications for studies on arsenic metabolism and toxicity. Chem Res Toxicol 17:1086–1091
Hirano S, Cui X, Li S, Kanno S, Kobayashi Y, Hayakawa T, Shraim A (2003) Difference in uptake and toxicity of trivalent and pentavalent inorganic arsenic in rat heart microvessel endothelial cells. Arch Toxicol 77:305–312
Hirano S, Kobayashi Y, Cui X, Kanno S, Hayakawa T, Shraim A (2004) The accumulation and toxicity of methylated arsenicals in endothelial cells: important roles of thiol compounds. Toxicol Appl Pharmacol 198:458–467
Hu CJ, Zhang AH, Huang HH (2003) Molecular pathology of skin carcinogenesis due to arsenicalism from coal-burning. Arch Environ Health 58:92–96
Kala SV, Neely MW, Kala G, Prater CI, Atwood DW, Rice JS, Lieberman MW (2000) The MRP2/cMOAT transporter and arsenic-glutathione complex formation are required for biliary excretion of arsenic. J Biol Chem 275:33404–33408
Kato K, Yamanaka K, Hasegawa A, Okada S (2003) Active arsenic species produced by GSH-dependent reduction of dimethylarsinic acid cause micronuclei formation in peripheral reticulocytes of mice. Mutat Res 539:55–63
Lin S, Shi Q, Nix FB, Styblo M, Beck MA, Herbin-Davist KM, Hall LL, Simeonsson JB, Thomas DJ (2002) A novel S-adenosyl-l-methionine: arsenic(III) methyltransferase from rat liver cytosol. J Biol Chem 277:10795–10803
Mandal BK, Ogra Y, Suzuki KT (2001) Identification of dimethylarsinous and monomethylarsonous acids in human urine of the arsenic-affected areas in West Bengal, India. Chem Res Toxicol 14:371–378
Nemeti B, Gregus Z (2002) Reduction of arsenate to arsenite in hepatic cytosol. Toxicol Sci 70:4–12
Petrick JS, Ayala-Fierro F, Cullen WR, Carter DE, Aposhian HV (2000) Monomethylarsonous acid (MMA(III)) is more toxic than arsenite in Chang human hepatocytes. Toxicol Appl Pharmacol 163:203–207
Radabaugh TR, Sampayo-Reyes A, Zakharyan RA, Aposhian HV (2002) Arsenate reductase II. Purine nucleoside phosphorylase in the presence of dihydrolipoic acid is a route for reduction of arsenate to arsenite in mammalian systems. Chem Res Toxicol 15:692–698
Reay PF, Asher CJ (1977) Preparation and purification of 74As-labeled arsenate and arsenite for use in biological experiments. Anal Biochem 78:557–560
Sampayo-Reyes A, Zakharyan RA, Healy SM, Aposhian HV (2000) Monomethylarsonic acid reductase and monomethylarsonous acid in hamster tissue. Chem Res Toxicol 13:1181–1186
Scott N, Hatlelid KM, Mackenzie NE, Carter DE (1993) Reactions of arsenic(III) and arsenic(V) species with glutathione. Chem Res Toxicol 6:102–106
Shraim A, Sekaran NC, Anuradha CD, Hirano S (2002) Speciation of arsenic in tube-well water samples collected from West Bengal, India, by high-performance liquid chromatography-inductively coupled plasma mass spectrometry. Appl Organomet Chem 16:202–209
Shraim A, Cui X, Li S, Ng JC, Wang HP, Jin YL, Liu YC, Guo L, Li DS, Wang SQ, Zhang RZ, Hirano S (2003) Arsenic speciation in the urine and hair of individuals exposed to airborne arsenic through coal-burning in Guizhou, PR China. Toxicol Lett 137:35–48
Styblo M, Thomas DJ (1997) Binding of arsenicals to proteins in an in vitro methylation system. Toxicol Appl Pharmacol 147:1-8
Styblo M, Delnomdedieu M, Thomas DJ (1996) Mono- and dimethylation of arsenic in rat liver cytosol in vitro. Chem Biol Int 99:147–164
Styblo M, Del Razo LM, Vega L, Germolec DR, LeCluyse EL, Hamilton GA, Reed W, Wang C, Cullen WR, Thomas DJ (2000) Comparative toxicity of trivalent and pentavalent inorganic and methylated arsenicals in rat and human cells. Arch Toxicol 74:289–299
Suzuki KT, Mandal BK, Katagiri A, Sakuma Y, Kawakami A, Ogra Y, Yamaguchi K, Sei Y, Yamanaka K, Anzai K, Ohmichi M, Takayama H, Aimi N (2004) Dimethylthioarsenicals as arsenic metabolites and their chemical preparations. Chem Res Toxicol 17:914–921
Tam GKH, Charbonneau SM, Bryce F, Pomroy C, Sandi E (1979) Metabolism of inorganic arsenic (74As) in humans following oral ingestion. Toxicol Appl Pharmacol 50:319–322
Vahter M, Marafante E, Dencker L (1984) Tissue distribution and retention of As-74-dimethylarsinic acid in mice and rats. Arch Environ Contam Toxicol 13:259–264
Walton FS, Waters SB, Jolley SL, LeCluyse EL, Thomas DJ, Styblo M (2003) Selenium compounds modulate the activity of recombinant rat As-III-methyltransferase and the methylation of arsenite by rat and human hepatocytes. Chem Res Toxicol 16:261–265
Waters SB, Devesa V, Del Razo LM, Styblo M, Thomas DJ (2004) Endogenous reductants support the catalytic function of recombinant rat Cyt19, an arsenic methyltransferase. Chem Res Toxicol 17:404–409
Wildfang E, Radabaugh TR, Aposhian HV (2001) Enzymatic methylation of arsenic compounds. IX. Liver arsenite methyltransferase and arsenate reductase activities in primates. Toxicology 168:213–221
Yamanaka K, Mizoi M, Tachikawa M, Hasegawa A, Hoshino M, Okada S (2003) Oxidative DNA damage following exposure to dimethylarsinous iodide: the formation of cis-thymine glycol. Toxicol Lett 143:145–153
Yamauchi H, Yamamura Y (1984) Metabolism and excretion of orally-administered dimethylarsinic acid in the hamster. Toxicol Appl Pharmacol 74:134–140
Zakharyan RA, Aposhian HV (1999) Arsenite methylation by methylvitamin B-12 and glutathione does not require an enzyme. Toxicol Appl Pharmacol 154:287–291
Zakharyan RA, Sampayo-Reyes A, Healy SM, Tsaprailis G, Board PG, Liebler DC, Aposhian HV (2001) Human monomethylarsonic acid (MMAV) reductase is a member of the glutathione-S-transferase superfamily. Chem Res Toxicol 14:1051–1057
Acknowledgements
This study was partially supported by Grant-in-aid for Scientific Research (14390058) from The Japan Society for Promotion of Science.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Hayakawa, T., Kobayashi, Y., Cui, X. et al. A new metabolic pathway of arsenite: arsenic–glutathione complexes are substrates for human arsenic methyltransferase Cyt19. Arch Toxicol 79, 183–191 (2005). https://doi.org/10.1007/s00204-004-0620-x
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00204-004-0620-x