Possible Interaction: Cysteine and Iodine

“We hypothesized … introduced cysteine pairs would be close enough for disulfide formation and would alter transport function: indeed, evidence for cross-link formation with low micromolar concentrations of copper phenanthroline or iodine was found in 3 of 8 initially tested pairs and in 1 of 26 additionally tested pairs.”

“ I and V react with the sulphydryl group of cysteine , and their activity may be related to inhibition of sulphydryl groups in cercarial enzymes.”

“Chlorine, bromine and iodine had the lowest propensity of interactions for cysteine , while fluorine had a lowest propensity for proline.”

“A hypothesis is advanced that half-cystine is oxidized by iodine to a normally unstable oxidation state which is maintained and protected by its protein invironment and that loss of tyrosine may be an artifact caused by the presence of this residue during acid hydrolysis.”

“The block to inhibition produced by mercurials was removed by the addition of cysteine or glutathione; the block to inhibition produced by iodine or iodoacetate was removed by cysteine , glutathione, NaHSO 3 , or Na 2 S 2 O 4 .”

“Cysteine and tryptophane are the only amino acids with reducing groups which are known to react with dilute iodine at pH 3.2 The reducing power of cysteine is abolished by the reaction with iodine , whereas the reducing power of tryptophane remains intact.”