P W Emery, King's College London, London, UK © 2005 Elsevier Ltd. All rights reserved.
Amino acids are generated within the body from three different sources. They enter the body from protein in the diet, and nonessential (dispensable) amino acids are synthesized from other metabolic intermediates, but by far the largest quantities of free amino acids arise from the breakdown of tissue proteins. Similarly, there are three metabolic fates for amino acids. Amino acid disposal is dominated by protein synthesis, but amino acids are also oxidized to carbon dioxide, water, and urea, or they may be metabolized to other small molecules. The pathways involved in each of these processes are considered, followed by a
Oxidation to urea
protein v acids ^ protein
Conversion to other compounds
Figure 1 Overview of amino acid metabolism.
discussion of the movement of amino acids between different compartments within the body (Figure 1).
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