Occurrence of GSH

Freshly pressed yeast is extracted by boiling twice with one-and-one-half times the amount of water, containing 0.1 % acetic acid. Some neutral lead acetate is added to the filtrate and then a 10% solution of mercuric sulfate in 5 % aqueous sulfuric acid. After decomposition of the Hg salt with H,S and removal of the excess H,S by a stream of an inert gas the solution is made 0.5 N with sulfuric acid and reprecipitated with CujO. This process precipitates GSH as a colorless crystalline copper salt. The decomposition with H,S yields 1 to 1.2 gm. of GSH from 1 kg. yeast. A method of isolation using the S-benzyl derivative has been published in 1941 (9). A Japanese patent (10) claims a fourfold yield after incubation of the yeast with cysteine and malt extract for 8 hours. 

Besides GSH the following similar peptides have been prepared a-L- 

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