Biochemistry

8.3 POISONOUS PROTEIN BREAKDOWN PRODUCTS IN THE INTESTINE AND THEIR DETOXIFICATION Amino acids that are not absorbed into the blood through the mucous membrane of the small intestine are exposed to microorganisms in the large intestine. At the same time, enzymes of microorganisms break down amino acids and turn them into amines, fatty acids, alcohols, phenols and other substances, often toxic to the body. Sometimes this process is called as rotting of proteins in the intestines. It is based on the decarboxylation of amino acids, while biological amines appear from amino acids. So, putrescine is formed from the ornithine amino acid: CHj - CH1 - CH 2 - CH - COOH — - CHi - CHj - CHi - CHj + co 2 1 1 1 1 NHj Nib Ж NIL Ornithine Putrescine Cadaverine is formed from lysine: NH 2 -CH - COOH NHj - (CHj) 5 - nh 2 + co 2 I (CH& I NH : Lysine (Cadaverijie Putrescine and cadaverine are excreted in the feces. In cases where these compounds enter the bloodstream, they are excreted unchanged in the urine. Poisonous substances are formed with a decay of cyclic amino acids in the colon, which after absorption through the intestines into the blood can have a strong physiological effect on the body. Cresol is formed from tyrosine, and if the process goes further, then phenol is formed: CH-COOH Cresol -CH 161