Amino acid metabolism
Stipanuk, Martha H. Division of Nutritional Sciences, Cornell University, Ithaca, New York.
Last reviewed:November 2018
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- Dietary amino acids
- Utilization of amino acids requires digestion and absorption
- Free amino acids
- Utilization of amino acids in the free amino acid pool
- Free amino acid pool and protein synthesis
- Synthesis of nonprotein compounds
- Carbon chains of amino acids
- Amino acid balance
- Related Primary Literature
- Additional Reading
The sum of the biochemical and physiological processes involved in the generation and degradation of amino acids, particularly those utilized as substrates for protein biosynthesis. Amino acid metabolism is a key biological activity undertaken by living organisms. Amino acids are organic compounds that possess one or more basic amino groups (—NH2) and one or more acidic carboxyl groups (—COOH) [Fig. 1]. Twenty amino acids serve as precursors or building blocks for the synthesis of proteins and peptides in the body. Proteins consist of linear polymers of amino acids, and they are synthesized by formation of peptide bonds between the carboxyl and amino groups of adjacent amino acids. Proteins make up approximately 17% of the body mass [about 12 kg (26.4 lb) in a 70-kg (154-lb) adult]. Amino acids also are necessary substrates for the synthesis of numerous nonprotein nitrogenous molecules, including nucleotides, creatine, heme, folate polyglutamates, epinephrine, and serotonin. In addition, they play important roles in the transport of nitrogen between organs. When amino acids are available in surplus of what is consumed for these synthetic processes, they are catabolized (broken down) to carbon compounds that are then either oxidized directly or used to synthesize glucose or triglycerides for storage or oxidation as fuels. See also: Amino acid; Biosynthesis; Energy metabolism; Metabolism; Peptide; Protein
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