LECTURE XII. 



ALBUMINS OR PROTEINS. 



VI. 

 METABOLIC END-PRODUCTS. 



WE have already mentioned the fact that putrefactive processes always 

 take place in the intestines to a greater or less extent. A part of the 

 products thus formed is absorbed and eliminated in the urine. Only a 

 small proportion of these compounds is excreted unchanged, or combined 

 with alkalies. By far the largest percentage of the albuminous cleavage- 

 products produced by putrefaction appear in the urine in the form of com- 

 plex combinations. Baumann l - and Brieger 2 have shown that here the 

 acid esters of sulphuric acid are most important. The organism produces 

 glucuronic acid only when there is a deficiency of sulphuric acid. There 

 always seems to be in the urine a small amount of conjugated glucuronic 

 acid compounds. The decomposition products are largely the aromatic 

 components of albumin; in fact, chiefly tyrosine and probably phenyl- 

 alanine as well. Tryptophane is likewise an important factor. We have 

 seen that tyrosine, which is p-hydroxyphenyl-a-aminopropionic acid, is 

 changed by loss of ammonia into p-hydroxyphenylpropionic acid; the 

 latter on further oxidation and loss of carbon dioxide finally decomposes 

 into p-cresol and phenol. From tryptophane skatole and indole are the 

 end-products obtained. 



The most important of the conjugated sulphuric acid compounds are 

 phenyl-, tolyl-, indoxyl-, and skatoxyl-sulphuric acids. Catechoyl-sul- 

 phuric acid is also, although not invariably, found in human urine in 

 small quantity. We may state that some of the sulphuric acid combina- 

 tions have not yet been identified. The amounts of such substances in 

 horse urine are especially large. In human urine, on the other hand, 

 there is much less present than of the other sulphur compounds. From 

 0.1-0.6 gram is excreted on an average every 24 hours. Experience has 

 shown that no definite values can be given. They vary considerably, and 

 are naturally dependent on the putrefactive changes in the intestines. 

 The excretion of the acid esters of sulphuric acid can be increased artifi- 



1 E. Baumann: Ber. 9, 54 (1876); 9, 1389 (1876); 9, 1715 (1876); 10, 685 (1877); 11, 

 1907 (1878); 12, 2166 (1879); Pfliiger's Arch. 12, 63 (1876); 12, 69 (1876); 13, 285 

 (1876); Z. physiol. Chem. 1, 60 (1877-78); 2, 335 (1878-79); 3, 250 (1879); 4, 304 (1880); 

 10, 123 (1886); 17, 511 (1893). 



2 E. Baumann and L. Brieger: ibid. 3, 254 (1879); 3, 156 (1879). 



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