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Title: Identification of an S-adenosylmethionine (SAM) dependent arsenic methyltransferase in Danio rerio

Abstract

Arsenic methylation is an important cellular metabolic process that modulates arsenic toxicity and carcinogenicity. Biomethylation of arsenic produces a series of mono-, di- and tri-methylated arsenic metabolites that can be detected in tissues and excretions. Here we report that zebrafish exposed to arsenite (As{sup III}) produces organic arsenicals, including MMA{sup III}, MMA{sup V} and DMA{sup V} with characteristic tissue ratios, demonstrating that an arsenic methylation pathway exists in zebrafish. In mammals, cellular inorganic arsenic is methylated by a SAM-dependent arsenic methyltransferase, AS3MT. A zebrafish arsenic methyltransferase homolog, As3mt, was identified by sequence alignment. Western blotting analysis showed that As3mt was universally expressed in zebrafish tissues. Prominent expression in liver and intestine correlated with methylated arsenic metabolites detected in those tissues. As3mt was expressed in and purified from Escherichia coli for in vitro functional studies. Our results demonstrated that As3mt methylated As{sup III} to DMA{sup V} as an end product and produced MMA{sup III} and MMA{sup V} as intermediates. The activity of As3mt was inhibited by elevated concentrations of the substrate As{sup III} as well as the metalloid selenite, which is a well-known antagonistic micronutrient of arsenic toxicity. The activity As3mt was abolished by substitution of either Cys160 or Cys210, whichmore » corresponds to conserved cysteine residues in AS3MT homologs, suggesting that they are involved in catalysis. Expression in zebrafish of an enzyme that has a similar function to human and rodent orthologs in catalyzing intracellular arsenic biomethylation validates the applicability of zebrafish as a valuable vertebrate model for understanding arsenic-associated diseases in humans. -- Highlights: ► Zebrafish methylated As{sup III} to MMA{sup III}, MMA{sup V} and DMA{sup V}. ► A zebrafish arsenic methyltransferase (As3mt) was purified in E. coli. ► As3mt catalyzed biomethylation of As{sup III} to DMA{sup V} and produced toxic intermediates. ► As3mt activity is inhibited by elevated substrate concentrations and selenite. ► C160 and C165 are predicted as As{sup III} binding sites.« less

Authors:
 [1]; ; ;  [2]; ;  [1];  [3];  [4];  [1]
  1. Department of Biological Sciences, Oakland University, Rochester, MI 48309 (United States)
  2. Department of Cellular Biology and Pharmacology, Herbert Wertheim College of Medicine, Florida International University, FL33199 (United States)
  3. Department of Medical Biotechnology and Laboratory Sciences, Chang-Gung University, Tao-Yuan, Kwei-San 333, Taiwan (China)
  4. School of Medical Laboratory and Biotechnology, Chung Shan Medical University, Taichung, Taiwan (China)
Publication Date:
OSTI Identifier:
22215361
Resource Type:
Journal Article
Journal Name:
Toxicology and Applied Pharmacology
Additional Journal Information:
Journal Volume: 262; Journal Issue: 2; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0041-008X
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; ANIMAL TISSUES; ARSENIC; CONCENTRATION RATIO; CYSTEINE; ESCHERICHIA COLI; EXCRETION; GLUTATHIONE; ICP MASS SPECTROSCOPY; IN VITRO; INTESTINES; LIVER; METABOLITES; METHYL TRANSFERASES; METHYLATION; RODENTS; TOXICITY

Citation Formats

Hamdi, Mohamad, Yoshinaga, Masafumi, Packianathan, Charles, Qin, Jie, Hallauer, Janell, McDermott, Joseph R., Yang, Hung-Chi, Tsai, Kan-Jen, and Liu, Zijuan. Identification of an S-adenosylmethionine (SAM) dependent arsenic methyltransferase in Danio rerio. United States: N. p., 2012. Web. doi:10.1016/J.TAAP.2012.04.035.
Hamdi, Mohamad, Yoshinaga, Masafumi, Packianathan, Charles, Qin, Jie, Hallauer, Janell, McDermott, Joseph R., Yang, Hung-Chi, Tsai, Kan-Jen, & Liu, Zijuan. Identification of an S-adenosylmethionine (SAM) dependent arsenic methyltransferase in Danio rerio. United States. https://doi.org/10.1016/J.TAAP.2012.04.035
Hamdi, Mohamad, Yoshinaga, Masafumi, Packianathan, Charles, Qin, Jie, Hallauer, Janell, McDermott, Joseph R., Yang, Hung-Chi, Tsai, Kan-Jen, and Liu, Zijuan. 2012. "Identification of an S-adenosylmethionine (SAM) dependent arsenic methyltransferase in Danio rerio". United States. https://doi.org/10.1016/J.TAAP.2012.04.035.
@article{osti_22215361,
title = {Identification of an S-adenosylmethionine (SAM) dependent arsenic methyltransferase in Danio rerio},
author = {Hamdi, Mohamad and Yoshinaga, Masafumi and Packianathan, Charles and Qin, Jie and Hallauer, Janell and McDermott, Joseph R. and Yang, Hung-Chi and Tsai, Kan-Jen and Liu, Zijuan},
abstractNote = {Arsenic methylation is an important cellular metabolic process that modulates arsenic toxicity and carcinogenicity. Biomethylation of arsenic produces a series of mono-, di- and tri-methylated arsenic metabolites that can be detected in tissues and excretions. Here we report that zebrafish exposed to arsenite (As{sup III}) produces organic arsenicals, including MMA{sup III}, MMA{sup V} and DMA{sup V} with characteristic tissue ratios, demonstrating that an arsenic methylation pathway exists in zebrafish. In mammals, cellular inorganic arsenic is methylated by a SAM-dependent arsenic methyltransferase, AS3MT. A zebrafish arsenic methyltransferase homolog, As3mt, was identified by sequence alignment. Western blotting analysis showed that As3mt was universally expressed in zebrafish tissues. Prominent expression in liver and intestine correlated with methylated arsenic metabolites detected in those tissues. As3mt was expressed in and purified from Escherichia coli for in vitro functional studies. Our results demonstrated that As3mt methylated As{sup III} to DMA{sup V} as an end product and produced MMA{sup III} and MMA{sup V} as intermediates. The activity of As3mt was inhibited by elevated concentrations of the substrate As{sup III} as well as the metalloid selenite, which is a well-known antagonistic micronutrient of arsenic toxicity. The activity As3mt was abolished by substitution of either Cys160 or Cys210, which corresponds to conserved cysteine residues in AS3MT homologs, suggesting that they are involved in catalysis. Expression in zebrafish of an enzyme that has a similar function to human and rodent orthologs in catalyzing intracellular arsenic biomethylation validates the applicability of zebrafish as a valuable vertebrate model for understanding arsenic-associated diseases in humans. -- Highlights: ► Zebrafish methylated As{sup III} to MMA{sup III}, MMA{sup V} and DMA{sup V}. ► A zebrafish arsenic methyltransferase (As3mt) was purified in E. coli. ► As3mt catalyzed biomethylation of As{sup III} to DMA{sup V} and produced toxic intermediates. ► As3mt activity is inhibited by elevated substrate concentrations and selenite. ► C160 and C165 are predicted as As{sup III} binding sites.},
doi = {10.1016/J.TAAP.2012.04.035},
url = {https://www.osti.gov/biblio/22215361}, journal = {Toxicology and Applied Pharmacology},
issn = {0041-008X},
number = 2,
volume = 262,
place = {United States},
year = {Sun Jul 15 00:00:00 EDT 2012},
month = {Sun Jul 15 00:00:00 EDT 2012}
}