Thompson J M, Nickels J S, Fisher J R
Biochim Biophys Acta. 1979 May 10;568(1):157-76. doi: 10.1016/0005-2744(79)90283-3.
The present study describes the (xanthine:NAD+ oxidoreductase, EC 1.2.1.37) synthesis and degradation of chick liver xanthine dehydrogenase in vivo and in organ cultures. The results indicate that control of xanthine dehydrogenase activity is mediated by changes in the rate of enzyme synthesis, but that degradation rates are unaffected. The results also suggest that xanthine dehydrogenase synthesis occurs through a previously unreported intermediate. Detected in cultures of liver tissue, this intermediate apparently is not converted into an active enzyme. A model of synthesis and degradation for xanthine dehydrogenase proposes that the synthesis of the enzyme is proportional to messenger RNA and includes an inactive enzyme precursor and a second inactive intermediate prior to degradation. Integrated mathematical solutions describing the concentration of intermediates as a function of time can be found explicitly for simple models. The appendix to this paper extrapolates solutions for one-, two- and three-step models to generate a mathematical solution for an 'n'-step model containing 'n' intermediates. The rate constants in the solutions can be found experimentally.
本研究描述了鸡肝黄嘌呤脱氢酶（黄嘌呤：NAD+氧化还原酶，EC 1.2.1.37）在体内和器官培养中的合成与降解。结果表明，黄嘌呤脱氢酶活性的调控是由酶合成速率的变化介导的，但降解速率不受影响。结果还表明，黄嘌呤脱氢酶的合成通过一种以前未报道的中间体进行。在肝组织培养物中检测到该中间体，它显然不会转化为活性酶。黄嘌呤脱氢酶的合成与降解模型提出，该酶的合成与信使RNA成正比，并且在降解之前包括一种无活性的酶前体和第二种无活性中间体。对于简单模型，可以明确找到描述中间体浓度随时间变化的综合数学解。本文附录将一步、两步和三步模型的解进行外推，以生成包含“n”个中间体的“n”步模型的数学解。解中的速率常数可通过实验获得。
