Biochemistry, Ammonia

Excerpt

Ammonia production occurs in all tissues of the body during the metabolism of a variety of compounds. Ammonia is produced by metabolizing amino acids and other compounds containing nitrogen. Ammonia exists as an ammonium ion (NH4⁺) at the physiological pH. It is produced in our body mainly by transamination followed by deamination from biogenic amines, from amino groups of nitrogenous bases like purine and pyrimidine, and in the intestine by intestinal bacterial flora through urease action on urea. Ammonia disposal takes place primarily by the hepatic formation of urea. The blood level of ammonia must remain very low because even slightly elevated concentrations (hyperammonemia) are toxic to the central nervous system. A metabolic mechanism exists by which nitrogen is moved from peripheral tissues to the liver for its ultimate disposal as urea while maintaining low circulating ammonia levels.