Influence of dietary protein levels on beta-alanine aminotransferase expression and activity in rats.
beta-Alanine-oxoglutarate aminotransferase (beta-AlaAT I) and beta-alanine-pyruvate aminotransferase (beta-AlaAT II) 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 I and beta-AlaAT II 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 I 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 II activity in the kidney was slightly decreased by a protein-free diet. Neither beta-AlaAT I nor beta-AlaAT II 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 proteinfree 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 I activity was not altered by the dietary protein level or by the beta-alanine diet, and beta-AlaAT II activity was not detected.
Ito
S
S
Laboratory of Nutritional Chemistry, Faculty of Nutrition and High Technology Research Center Kobe-Gakuin University, Kobe, Japan.
Ohyama
T
T
Kontani
Y
Y
Matslida
K
K
Sakata
S F
SF
Tamaki
N
N
D000410:Alanine Transaminase / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D015091:beta-Alanine / Q000008:administration & dosage* / Q000378:metabolism*
D004044:Dietary Proteins; D015091:beta-Alanine; D000410:Alanine Transaminase