Tamaki N, Fujimoto S, Mizota C, Kaneko M, Kikugawa M
Laboratory of Nutritional Chemistry, Faculty of Nutrition, Kobe-Gakuin University, Japan.
J Nutr Sci Vitaminol (Tokyo). 1989 Oct;35(5):451-61. doi: 10.3177/jnsv.35.451.
The effect of 6-azauracil on beta-alanine metabolism was investigated in vivo in the rat. Both of the enzymes beta-alanine-oxoglutarate aminotransferase (aminobutyrate aminotransferase) and D-3-aminoisobutyrate-pyruvate aminotransferase [R)-3-amino-2-methylpropionate-pyruvate aminotransferase), which are beta-alanine catabolizing enzymes from rat liver and kidney, were inactivated by 6-azauracil injection, while dihydrouracil dehydrogenase, dihydropyrimidinase, and beta-ureidopropionase, which are pyrimidine metabolizing enzymes, were not affected. The content of beta-alanine was increased, but the level of uridine and uracil in rat liver was not affected, by 6-azauracil. When a crude enzyme preparation was passed through a Sephacryl S-200 column, both enzymes could be separated from each other. beta-Alanine-oxoglutarate aminotransferase and beta-alanine-pyruvate aminotransferase activities in rat liver decreased to 27.4% and 63.9%, respectively, upon 6-azauracil injection, and those in kidney were 11.7% and 38.3%, respectively. From these findings, it is suggested that the accumulation of beta-alanine in 6-azauracil-treated rat liver might be caused by the inhibition of beta-alanine catabolizing enzymes, but not by an increase in the uridine pool nor by the activation of pyrimidine metabolism.
在大鼠体内研究了6-氮尿嘧啶对β-丙氨酸代谢的影响。来自大鼠肝脏和肾脏的β-丙氨酸分解代谢酶β-丙氨酸-酮戊二酸转氨酶（氨基丁酸转氨酶）和D-3-氨基异丁酸-丙酮酸转氨酶[（R）-3-氨基-2-甲基丙酸-丙酮酸转氨酶]，在注射6-氮尿嘧啶后均被灭活，而嘧啶代谢酶二氢尿嘧啶脱氢酶、二氢嘧啶酶和β-脲基丙酸酶未受影响。6-氮尿嘧啶使大鼠肝脏中β-丙氨酸含量增加，但尿苷和尿嘧啶水平未受影响。当粗酶制剂通过Sephacryl S-200柱时，两种酶可以彼此分离。注射6-氮尿嘧啶后，大鼠肝脏中β-丙氨酸-酮戊二酸转氨酶和β-丙氨酸-丙酮酸转氨酶活性分别降至27.4%和63.9%，肾脏中的活性分别为11.7%和38.3%。从这些发现可以推测，6-氮尿嘧啶处理的大鼠肝脏中β-丙氨酸的积累可能是由于β-丙氨酸分解代谢酶受到抑制，而不是由于尿苷池增加或嘧啶代谢激活所致。
