BACTERIAL DIGESTION IN THE INTESTIK 503 



Bacterial Digestion of Protein 



From a pathological standpoint, the most importanl action of bacteria 

 is thai which takes place on protein. Under anaerobic conditions the 

 intestinal bacteria have in general the power of splitting off the amino 

 group whereas under aerobic conditions they split off the carboxyl 

 group. This splitting off of the carboxyl group as carbon dioxide is | 

 formed by the so-called carboxj lase bacteria, and it may tak< either 



before or after deamidization se< pi 615 . It' it happens after this 



process, the products are no1 highly toxic and include phenol, cresol, 

 indole and skatole, which are partly absorbed into the blood ami partly 

 excreted with the feci - 



The fractions of those substances thai are absorbed into the blood 

 have their toxicity removed by conjugation mainly with sulphuric acid 

 to form tho so-called ethereal sulphates. A pari is also combined with 

 glycuronic acid (see page 632). In the case of phenol and cresol this 

 conjugation occurs immediately after absorption, but in the <• n 

 indole and skatole it is preceded by an oxidative pro converting 



these substances into indoxy] and skatoxyl respectively. The detoxica- 



tion pr iss occurs in the liver, as has been shewn by experiments in 



which this organ was artificially perfused outside the body. Thi 



then removed from the M 1 by the kidneys and excreted in the urine. 



The proportion of ethereal sulphates in this fluid is therefore an indica- 

 tion of the extent of intestinal putrefaction of protein e I 12 

 The indican, being readily detectable by the well-known color reaction 

 of Jaffe", sen an indicator of the extent of intestinal putrefaction. 

 The indole ami skat«»le which are not thus absorbed ami detoxicated are 

 excreted with the feces, i<> which they give the characteristic ndor. 



The source of the phenol is tyrosine and that of the indole is try;' 



phane. The chein ica 1 pi - involved are shown in the following 



equations, in which the by-products of the rei - arc in brackets 



i ih COB I "II • "II >H 



//\ // 



Ih • ii in en in- <-n in- .11 in • CH 



lie ill lie CH HC « II IK' 'II HC 



. || CH "II ; l" 



Ml 

 "IIMI ('II """II 



I 

 OH "II 



oxyphenyl enyl 



propionic a. 



