Wu J M, Nickels J S, Fisher J R
Enzyme. 1977;22(1):60-9. doi: 10.1159/000458509.
Previous studies have shown that a group of nitrogen catabolic enzymes including xanthine dehydrogenase, purine nucleoside phosphorylase, and tyrosine aminotransferase are all increased in chick liver by dietary protein as well as single amino acids (e.g. methionine) and certain antimetabolites (e.g. hydrazine). A similar enzyme response pattern can be obtained with insulin. This hormone causes an enhanced rate of XDH synthesis and gives nonadditive results with protein, hydrazine and methionine. Furthermore, a vitamin B6 dependency was observed in responses to both high protein diets and insulin, all suggesting a common regulatory mechanism. In this system dietary protein and insulin may act similarly by increasing the availability of amino acids to the liver -- in one case by supplying amino acids through the diet and in the other by increasing amino acid uptake.
先前的研究表明，包括黄嘌呤脱氢酶、嘌呤核苷磷酸化酶和酪氨酸转氨酶在内的一组氮分解代谢酶，在雏鸡肝脏中都会因膳食蛋白质、单个氨基酸（如蛋氨酸）和某些抗代谢物（如肼）而增加。胰岛素也能产生类似的酶反应模式。这种激素会提高黄嘌呤脱氢酶的合成速率，并且与蛋白质、肼和蛋氨酸产生非累加性结果。此外，在对高蛋白饮食和胰岛素的反应中都观察到了维生素B6依赖性，这一切都表明存在一种共同的调节机制。在这个系统中，膳食蛋白质和胰岛素可能通过增加肝脏可利用的氨基酸起类似作用——一种情况是通过饮食提供氨基酸，另一种情况是通过增加氨基酸摄取。
