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Asparagine

Asparagine

Description

Asparagine is a nonessential amino acid, which means it is manufactured from other amino acids in the liver; it does not have to be obtained directly through the diet.

There is no suggested need for asparagine supplementation presently available in the literature. Asparagine is interrelated with the amino acid aspartic acid. Low levels of asparagine may indicate poor metabolism or synthesis of aspartic acid, which can result in the inability to properly synthesize and excrete urea, which is the major waste product of excess dietary protein. The inability to excrete urea can result in buildup of nitrogen-containing toxic metabolites that can lead to confusion, headaches, depression, irritability, or, in extreme cases, psychosis.

Deficiencies of nonessential amino acid will not occur if a well-balanced diet is consumed because the intake of proper foods will allow the body to produce exactly the amount of amino acid required to function optimally.

Recommended Dietary Allowances

An RDA has not been established for asparagine because it is a nonessential amino acid.

Food Sources

Asparagine is a nonessential amino acid, which means it is manufactured from other amino acids in the liver; it does not have to be obtained directly through the diet.

Method of Action

Prior to 1940, amino acids were generally regarded as relatively-stable nutrient building blocks. In the 1940s and '50s that concept was abandoned when it was found that the nitrogen atom in amino acids such as aspartic and glutamic acids could be rapidly converted from one amino acid carbon skeleton to another.

The process by which these nitrogen atoms are exchanged is called transamination and is dependent upon the coenzyme pyridoxal pyrophosphate, which is derived from vitamin B-6. Both aspartic acid and glutamic acid can incorporate ammonia, thereby resulting in the production of asparagine and glutamine, respectively. It soon became apparent asparagine and glutamine are soluble, nontoxic carriers of additional ammonia in the form of their amid groups.

An active enzyme converts aspartate and ammonia to asparagine and glutamate and ammonia to glutamine. The nitrogen in glutamine is used in a great variety of biochemical processes, including the formation of carbamoyl phosphate used in the urea cycle and the production of purines, which are used in DNA and RNA.

Glutamate, glutamine, and aspartate also play central roles in the removal of all nitrogen from organic compounds. The exchange of nitrogen by transamination is reversible so when the body is properly managing glutamate and aspartate, there is the exchange of nitrogen from one source, ultimately, from the urea cycle and the elimination in the urine as urea.

Abstracts

References

Li, J.B. & Jefferson, L.S. Influence of Amino Acid Availability on Protein Turnover in Perfused Skeletal Muscle. Biochim. Biphys. Acta., 544:351-9, 1978.

Munro, H.N. & Crim, M.C. The Proteins and Amino Acids. Modern Nutrition in Health and Disease. eds. R.S. Goodhart & M.E. Shils, 6 ed., Phila. Lea and Febiger, 1980.

Rudman, D., Galambos, J.T., Smith, R.B., Iii, Salam, A.A., & Warren, W.D., Comparison of the Effect of Various Amino Acids upon the Blood Ammonia Concentration of Patients with Liver Disease. Am. J. Clin. Nutr., 26:916-25, 1973.

Windmueller, H.G. & Spaeth, A.E. Metabolism of Absorbed Aspartate, Asparagine, and Arginine by Rat Small Intestine In Vivo. Arch. Biochem. Biophys., 175:670-6, 1976.

Young, V.R., Meguid, M., Meredith, D.E., & Bier, D.M. Recent Developments in Knowledge of Human Amino Acid Requirements. Nitrogen Metabolism in Man. eds. J.C. Waterlow & J.M.L. Stephen. London, Applied Science Pub. 1981.

 


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