Why Threonine Is an Essential Amino Acid in Mammals and Birds: Studies at the Enzyme Level
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The only pathway for the synthesis of essential amino acids in vertebrates is reversible transamination of their keto analogs with glutamic acid. At the same time, it is commonly accepted that such essential amino acids as lysine and threonine are not involved in transamination and, therefore, cannot be synthesized from their keto analogs. However, using radio-labeled isotopes, synthesis of threonine was demonstrated in rat liver and in a reaction mixture containing chicken liver threonine dehydrogenase. In the review, we discuss why threonine is an essential amino acid in mammals and birds based on the pathways of threonine biosynthesis in these two classes of vertebrates.
Keywordsthreonine NAD acetyl-CoA threonine dehydrogenase threonine dehydratase
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- 3.Meister, A. (1961) Biochemistry of the Amino Acids [Russian translation], Inostrannaya Literatura, Moscow.Google Scholar
- 5.Aoyama, Y., and Motokava, Y. (1981) L–Threonine dehy–drogenase of chicken liver, Biol. Chem., 256, 12367.Google Scholar
- 9.Pagani, R., Guerranti, R., Leoncini, R., and Marinello, E. (1990) Activation and inhibition of rat liver L–threonine dehydrogenase, Ital. J. Biochem., 39, 108.Google Scholar
- 12.Berezov, T. T. (1969) Metabolism of Amino Acids in Normal Tissues and Malignant Tumors [in Russian], Meditsina, Moscow.Google Scholar
- 18.D’Mello, J. P. F. (1973) Aspects of threonine and glycine metabolism in the chick (Gallus domesticus), J. Nutr., 15, 357–363.Google Scholar
- 20.Watanabe, R., Fujimura, S., Kadowaki, M., and Ishibashi, T. (1998) Effects of dietary threonine levels on the threo–nine–degrading enzyme activities and tissue threonine related amino acid concentration in rats, Anim. Sci. Technol. (Jpn), 69, 108–116.Google Scholar