Comparative studies of ‘bile salts’. 1. Preliminary survey

PART 2 5.The reaction kinetics of the hydrolytic decom- position of G2S2 and cystine in the presence of an excess of silver nitrate were studied under various conditions.The reactions were classified into three main types.6. Acetate was shown to catalyse the reaction of cystine and, to a much lesser extent, that of.G2S2.Similarly, barbitone inhibited the cystine reaction completely, but that of G2S2 only slightly.7. In the presence of GSH and G2S2, cystine was shown to behave in a manner resembling G2S2.8. Tentative explanations for the three different types of reaction kinetics are put forward.9.A possible explanation for the greater re- activity of the sulphur in GSH and G2S2 as compared with that in cysteine in cystine is given.This involves a hydrogen bond between the sulphur in GSH and G2S2 and the -NH3+ group of the glutamyl radical.My thanks are due to Dr A. G. Ogston for much helpful advice, and to Dr R. B. Fisher for the gift of glutathione.Correction.Subsequent work has disclosed an impurity in the a-picoline used in Part 2 of this work.The cystine- silver nitrate reaction carried out with purified a-picoline at pH7-0 is Type II and not Type III.Curve C in Fig. 7 becomes intermediate between curves A and D. No other results are affected.Details will be given in a later publication.