On the Preparation and Properties of Pure Glutathione (glutaminyl-cysteine)

Glutathione was first. isolated in 1921 from yeast, mammalian liver, and muscle by Hopkins (5), who also presented evidence indicating that the substance is a dipeptide of cysteine and glutamic acid. In 1925 Stewart and Tunnicliffe (8) published their work on the synthesis of glutathione. Their second synthetic method yielded a product, which possessed all of the properties of the substance found in nature. Since then, a number of other workers have prepared the natural product, but so far no analytic findings have been published which would support the data given by the English investigators. Brand and Sandberg (3), for instance, obtained a product from ox blood with a sulfur tiontent of 8.6 per cent instead of the theoretical figure of 12.87 per cent. They therefore considered their substance impure. The other workers, with the exception of Hunter and Eagles (7), do not give any analytical findings at all. About a year ago there appeared a paper by Hunter and Eagles (7) which led these workers to the conclusion that glutathione prepared from yeast, blood, and liver in reality is not a simple dipeptide composed of cysteine and glutamic acid, but more likely a tripeptide of Iunknown composition. They base this conclusion largely on the fact that their products had a much lower sulfur and higher total nitrogen content than the products of the English workers. Hunter and Eagles’ report was immediately followed by a short note by Hopkins (6) in which he suggests that the low sulfur content of the products obtained by Hunter and Eagles was probably due to the splitting off of sulfur from the substance by the alkali used in the course of isolation. Bergmann and Stather (2) had previously called attention to the great ease with which alkali splits off sulfur from dialanyl-Z-cystine dianhydride. Referring to this work Hopkins in his note reported some experiments which indicate that exposure of pure glutathione to alkali results in the splitting off of sulfur. He concludes with the following remarks: “In any case, although I have myself no doubt as to the nature of glutathione, the appearance of Hunter and Eagles’ papers makes it desirable that I should if possible give greater precision to the account of its isolation. This I hope to do in the near future.”