ALBUMINS OR PROTEINS. 159 



products, Baumann and Preusse proposed the following formula of 

 mercapturic acid: 



CH 3 



CH 3 CO NH . C S . C 6 H 4 Br 



If this formula be correct, then it must correspond to a differently 

 constituted cysteine than the above one. We might expect that cystine 

 could occur in various modifications. E. Friedmann, 1 proceeding from this 

 hypothesis, undertook to prove the constitution of mercapturic acid, and 

 showed that such an assumption was unnecessary, for he found that mer- 

 capturic acid and cysteine have their amino and thio groups analogously 

 situated: 



CH2 . SH CH2 . S . CgH^X 



CH . NH 2 CH . NH . CO . CH 3 



CO( 



>OH COOH 



Albumin-cysteine Mercapturic acid 



Recent investigations have also shown that probably only one cysteine 

 exists. 2 Patten 3 has shown that only cystine and not cysteine occurs in the 

 original albumin molecule. 



It is necessary to mention at this point that all the compounds so far 

 discussed, with the exception of phenylalanine, can also be obtained by 

 the hydrolytic action of ferments upon the albumins. Phenylalanine, as 

 already indicated, is found as such in plant seeds. As fermentation 

 hydrolysis undoubtedly furnishes the mildest possible form of decom- 

 position, we are justified in concluding that the cleavage-products of 

 protein which have been just mentioned exist as such in the albumin 

 molecule. 



While discussing the proteids, we mentioned the so-called " gluco- 

 proteids " of the albumins, which are characterized by a high percentage 

 of glucosamine, and, possibly, other carbohydrates. On account of the 

 firmness with which these groups are attached to the albumin molecule, 

 it is at present considered more correct to place them with the simpler 

 proteins rather than with the complex varieties. We can easily imagine 

 that glucosamine is held in combination in a manner analogous to that 

 which unites the amino acids to one another. We can also easily indicate 



1 E. Friedmann: Hofmeister's Beitr. 4, 486 (1903). 



3 E. Fischer and U. Suzuki: Z. physiol. Chem. 45, 405 (1905). 



8 A. J. Patten: find. 39 350 (1903). 



