Iodoacetamide

2-Iodoacetamide is an alkylating agent used for peptide mapping purposes. Its actions are similar to those of iodoacetate. It is commonly used to bind covalently with the thiol group of cysteine so the protein cannot form disulfide bonds.[1][2] Also used in ubiquitin studies as an inhibitor of deubiquitinase enzymes (DUBs) because it alkylates the cysteine residues at the DUB active site.

Iodoacetamide
Names
Preferred IUPAC name
2-Iodoacetamide
Identifiers
3D model (JSmol)
ChEMBL
ChemSpider
ECHA InfoCard 100.005.119
EC Number
  • 205-630-1
RTECS number
  • AC4200000
UNII
Properties
C2H4INO
Molar mass 184.964 g·mol−1
Appearance white crystals (yellow colouration indicates the presence of iodine)
Melting point 94 °C (201 °F; 367 K)
Hazards
Safety data sheet MSDS 1, MSDS 2
NFPA 704 (fire diamond)
Flammability code 0: Will not burn. E.g. waterHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no code
0
3
1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Peptidase inhibitor

Iodoacetamide 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 acid derivative, iodoacetate, iodoacetamide reacts substantially faster. 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 iodoacetate is the reason for the increased relative activity of iodoacetamide.[3]

Mechanism of irreversible inhibition of cysteine peptidases with iodoacetamide.

Protein mass spectrometry

It is commonly used during the sample preparation for de novo (peptide) sequencing with protein mass spectrometry, but recent critics suggest to avoid the use of it [4]

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References
  1. Smythe CV (1936). "The reactions of Iodoacetate and of Iodoacetamide with various Sulfhydryl groups, with Urease, and with Yeast preparations". J. Biol. Chem. 114 (3): 601–12.
  2. Anson ML (1940). "The reactions of Iodine and Iodoacetamide with native Egg Albumin". J. Gen. Physiol. 23 (3): 321–31. doi:10.1085/jgp.23.3.321. PMC 2237930. PMID 19873158.
  3. Polgar, L (1979). "Deuterium isotope effects on papain acylation. Evidence for lack of general base catalysis and for enzyme-leaving group. interaction". Eur. J. Biochem. 98 (2): 369–374. doi:10.1111/j.1432-1033.1979.tb13196.x. PMID 488108.
  4. Müller (2017). "Systematic Evaluation of Protein Reduction and Alkylation Reveals Massive Unspecific Side Effects by Iodine-containing Reagents". Molecular & Cellular Proteomics. 16 (7): 1173–1187. doi:10.1074/mcp.M116.064048. PMC 5500753. PMID 28539326.
  • The MEROPS online database for peptidases and their inhibitors:
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