抄録
Native or urea-denatured egg albumin was allowed to react with C3H7SSC3H7 (I) or C3H7SSOC3H7 (II) under a certain condition. The protein was precipitated by ethanol treatment and the unreacted I or II was completely removed by extracting the precipitate several times with hot ethanol. The protein fraction was reduced by cysteine, producing the free propylmercaptan. It is assumed to have been produced from the compound bound with the protein similarly to S-propylmercapto-cysteine. As the microdetermination of propylmercaptan was possible by utilizing dithizon method, the amount of the bound propylmercaptan under various contions was investigated and the following results were obtained.
1. The formation of the bound form of I was markedly increased by protein denaturation, producing also the free propylmercaptans. The formation of the bound form of II was somewhat increased after denaturation of the protein, but was observed significantly with the native protein. In this case the formation of free propylmercaptan was scarcely observed.
2. The reaction of I with the protein was markedly dependent on pH levels, rising definitely at pH levels above 7.0. On the other hand, the reaction of II was little affected by pH levels, showing almost a constant activity at pH range above 6.0.
3. The reactivity of I or II was increased with the rise of temperature and time.
4. When the SH-groups of the protein were oxidized with iodine or blocked by p-chloromercuribenzoate, the reactivity was remarkably reduced.
These findings suggest that the compound I or II, though the reaction mechanisms are different from each other, reacts with the SH-groups of the protein, forming a protein-bound compound like protein-SS-C3H7.
