Influence of dietary protein levels on beta-alanine aminotransferase expression and activity in rats
2001
Ito, S. (Kobe Gakuin Univ. (Japan). Faculty of Nutrition) | Ohyama, T. | Kontani, Y. | Matsuda, K. | Fujimoto Sakata, S. | Tamaki, N.
Beta-Alanine-oxoglutarate aminotransferase (beta-AlaAT 1) and beta-alanine-pyru-vate aminotransferase (beta-AlaAT 2) catalyze the transamination reaction of omega-amino acids such as beta-alanine, beta-aminoisobutyrate, and gamma-aminobutyrate, amino acids that are not protein constituents. The influence of dietary protein levels on the expression and activities of these enzymes was investigated by using male rats. Both beta-AlaAT 1 and beta-AlaAT 2 activities in the liver were increased with the level of protein in the diet in accordance with changes in their mRNA levels. However, the beta-AlaAT 1 activity in the kidney was increased by protein-free and low-protein diets in relation to changes in its mRNA level. On the other hand, the level of beta-AlaAT 2 activity in the kidney was slightly decreased by a protein-free diet. Neither beta-AlaAT 1 nor beta-AlaAT 2 activities in the kidney were affected by a high-protein diet. These results suggested that beta-alanine may be used efficiently in animals fed a protein-free or low-protein diet because the kidney provides beta-alanine by means of the hydrolysis of beta-alanyl-L-histidine (carnosine). The addition of beta-alanine to the diet significantly activated beta-AlaAT I in the kidneys of rats in accordance with changes in its mRNA level. In the rat brain, beta-AlaAT 1 activity was not altered by the dietary protein level or by the beta-alanine diet, and beta-AlaAT 2 activity was not detected.
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