Oxidative Scission of the Disulfide Bond of Cystine and Polypeptides by the Action of Allyl Isothiocyanate

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The interaction of allyl isothiocyanate (1) with L-cystine and polypeptides under mild conditions was studied in detail. The reaction mixtures composed of isothiocyanate and cystine were incubated at 40, 60 and 80°C, in which cystine completely decomposed after 120, 6 and 2hr, respectively. Degradation products were isolated and identified as 2-allylamino-2-thiazoline-4-carboxylic acid (2), 2-amino-2-thiazoline-4-carboxylic acid (3) and 3(3H)-allyl-5, 6-dihydro-5-amino-2(2H)-thioxo-1, 3-thiazin-4-one (4). These products were formed through an oxidative scission of the disulfide bond in cystine by the electrophilic attack of allyl isothiocyanate; the products 2 and 4 seemed to be derived through alanyl N-allyldithiocarbamate and the product 3 through β-thiocyanoalanine. In addition, it was confirmed that a part of the disulfide bond in oxidized glutathione and insulin was also cleaved by isothiocyanate.