Ammonia production occurs in all tissues of the body during the metabolism of a variety of compounds. Ammonia is produced by the metabolism of amino acids and other compounds which contain nitrogen. Ammonia exists as ammonium ion (NH4+) at the physiological pH and is produced in our body mainly by the process of transamination followed by deamination, from biogenic amines, from amino groups of nitrogenous base like purine and pyrimidine, and in the intestine by intestinal bacterial flora through the action of urease 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 (CNS). A metabolic mechanism exists by which nitrogen is moved from peripheral tissues to the liver for its ultimate disposal as urea, while at the same time maintaining low levels of circulating ammonia.
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