Iodoacetic acid

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Iodoacetic acid
Skeletal formula
Space-filling model
64-69-7 YesY
ChEMBL ChEMBL376280 YesY
ChemSpider 5050 YesY
Jmol interactive 3D Image
PubChem 5240
Molar mass 185.95 g·mol−1
Melting point 81 °C (178 °F; 354 K)
Boiling point 208 °C (406 °F; 481 K)
Safety data sheet Oxford MSDS
Toxic (T); Corrosive (C)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Iodoacetic acid is a derivative of acetic acid. It is a toxic compound, because, like many alkyl halides, it is an alkylating agent. It reacts with cysteine residues in proteins. It is often used to modify SH-groups to prevent the re-formation of disulfide bonds after the reduction of cystine residues to cysteine during protein sequencing.

Peptidase inhibitor[edit]

Iodoacetate is an irreversible inhibitor of all cysteine peptidases, with the mechanism of inhibition occurring from alkylation of the catalytic cysteine residue (see schematic). In comparison with its amide derivative, iodoacetamide, iodoacetate reacts substantially slower. This observation appears contradictory to standard chemical reactivity, however the presence of a favourable interaction between the positive imidazolium ion of the catalytic histidine and the negatively charged carboxyl-group of the iodoacetic acid is the reason for the increased activity of iodoacetamide.[1]

Mechanism of irreversible inhibition of cysteine peptidases with iodoacetate.

Possible cancer therapy[edit]

Several studies have shown iodoacetate has anti-tumor effects. In 2002 Dr. Fawzia Fahim showed that "a single IAA treatment of tumor-bearing mice significantly increased the levels of plasma lactate dehydrogenase (LDH) activity, while it also significantly decreased the levels of plasma glucose and liver total protein, RNA and DNA, compared to normal controls."[2] In 1975 Melvin S. Rhein, Joyce A. Filppi and Victor S. Moore showed that iodoacetate improved the immune response of bone marrow.[3] In 1966 Charles A. Apffel, Barry G. Arnason & John H. Peters showed anti-tumor activity for iodoacetate.[4]

As a disinfection by-product[edit]

Iodide is a naturally occurring ion that can be found in many source waters and it is easily oxidized by wastewater disinfectants. One of the products of iodide oxidation is hypoiodous acid (HOI or OI) which is capable of reacting with background organic materials to generate iodinated disinfection by-products (DBPs) including iodoacetic acid. In a study performed by Plewa, et al., IAA was determined to be one of the most cytotoxic of those studied, with a median lethal dose on the order of magnitude of 10−5 M. It was the most genotoxic of more than 60 DBPs studied and is the most genotoxic DBP identified thus far.[5] Iodoacetic acid has exhibited traits indicating it as a potential carcinogen, however, it has not been proven to be carcinogenic.[6] The trend continues in teratogenicity, with iodoacetic acid’s potency surpassing that of its brominated and chlorinated analogs.[7] Its toxicity correlates to its ability as an alkylating agent, which will modify cysteine residues in proteins.[8] Monohaloacetic acids are the most toxic, with toxicity increasing with halogen size. Iodoacetic acid is more toxic than bromoacetic acid and much more toxic than chloroacetic acid.[9]

See also[edit]


  1. ^ Polgár, L. (1979). "Deuterium isotope effects on papain acylation. Evidence for lack of general base catalysis and for enzyme-leaving group interaction" (pdf). European Journal of Biochemistry 98 (2): 369–374. doi:10.1111/j.1432-1033.1979.tb13196.x. PMID 488108. 
  2. ^ Fahim, F. A.; Esmat, A. Y.; Mady, E. A.; Ibrahim, E. K. (2003). "Antitumor Activities of Iodoacetate and Dimethylsulphoxide Against Solid Ehrlich Carcinoma Growth in Mice". Biological Research 36 (2): 253–262. doi:10.4067/S0716-97602003000200015. PMID 14513720. 
  3. ^ Rhein, M. S.; Filppi, J. A.; Moore, V. S. (1975). "Effect of Iodoacetate on the Bone Marrow Immunocompetence of AKR Mice" (pdf). Cancer Research 35 (6): 1514–1519. PMID 1093673. 
  4. ^ Apffel, C. A.; Arnason, B. G.; Peters, J. H. (1966). "Induction of tumour immunity with tumour cells treated with iodoacetate". Nature 209 (5021): 694–696. Bibcode:1966Natur.209..694A. doi:10.1038/209694a0. PMID 5922128. 
  5. ^ Plewa, Michael J.; Wagner, Elizabeth D.; Richardson, Susan D.; Thruston, Alfred D., Jr.; Woo, Yin-Tak; McKague, A. Bruce (2004). "Chemical and Biological Characterization of Newly Discovered Iodoacid Drinking Water Disinfection Byproducts". Environmental Science & Technology 38 (18): 4713–4722. Bibcode:2004EnST...38.4713P. doi:10.1021/es049971v. 
  6. ^ Wei, Xiao; Wang, Shu; Zheng, Weiwei; Wang, Xia; Liu, Xiaolin; Jiang, Songhui; Pi, Jingbo; Zheng, Yuxin; He, Gengsheng; Qu, Weidong (2013). "Drinking Water Disinfection Byproduct Iodoacetic Acid Induces Tumorigenic Transformation of NIH3T3 Cells". Environmental Science & Technology 47: 5913–5920. doi:10.1021/es304786b. 
  7. ^ Richard, Ann M.; Hunter, E. Sidney, III (1996). "Quantitative Structure-Activity Relationships for the Developmental Toxicity of Haloacetic Acids in Mammalian Whole Embryo Culture". Teratology 53 (6): 352–360. doi:10.1002/(SICI)1096-9926(199606)53:6<352::AID-TERA6>3.0.CO;2-1. PMID 8910981. 
  8. ^ "Product #35603". Thermo Scientific. Pierce Protein Biology Products. 
  9. ^ Richardson, Susan D.; Plewa, Michael J.; Wagner, Elizabeth D.; Shoeny, Rita; DeMarini, David M (2007). "Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research". Mutation Research 636 (1–3): 178–242. doi:10.1016/j.mrrev.2007.09.001. PMID 17980649. 

Further reading[edit]

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