Ovothiol A

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Ovothiol A
Ovothiol A.svg
IUPAC name
(2S)-2-Amino-3-(3-methyl-5-sulfanylimidazol-4-yl)propanoic acid
Other names
3D model (Jmol) Interactive image
ChEBI CHEBI:83318 YesY
ChemSpider 115159
MeSH C061475
PubChem 130131
Molar mass 201.24 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Ovothiol A (N1-methyl-4-mercaptohistidine) is a highly reducing antioxidant mercaptohistidine, which accumulates to very high levels in the eggs of certain marine invertebrates, including sea urchins, scallops and starfish,[1] where it acts to scavenge hydrogen peroxide released during fertilization.[2]

This thiol is also found in some human pathogens including trypanosomes and members of the genus Leishmania.[3]

It is synthesized by the addition and oxidation of cysteine to histidine by 5-histidylcysteine sulfoxide synthase, followed by methylation and further reduction.


  1. ^ Turner, E., Klevit, R., Hager, L. J. & Shapiro, B. M.; Klevit; Hager; Shapiro (1987). "Ovothiols, a family of redox-active mercaptohistidine compounds from marine invertebrate eggs". Biochemistry. 26 (13): 4028–4036. doi:10.1021/bi00387a043. PMID 3651433. 
  2. ^ Turner, E., Hager, L. J. & Shapiro, B. M.; Hager; Shapiro (1988). "Ovothiol replaces glutathione-peroxidase as a hydrogen-peroxide scavenger in sea-urchin eggs". Science. 242 (4880): 939–941. doi:10.1126/science.3187533. PMID 3187533. 
  3. ^ Spies, H.S. & Steenkamp, D.J. (1994). "Thiols of intracellular pathogens. Identification of ovothiol A in Leishmania donovani and structural analysis of a novel thiol from Mycobacterium bovis". Eur. J. Biochem. 224 (1): 203–213. doi:10.1111/j.1432-1033.1994.tb20013.x. PMID 8076641.