Metabolic Control Analysis

人们普遍认为，主要代谢途径中的步骤是已知的，并且通过这些途径的通量控制发生在非常有限数量的“速率限制”步骤。 这一概念导致了药物的设计，以改变这些“限速酶”的动力学。 它还导致尝试通过使用分子生物学技术改变限速酶的量来改变代谢途径。 令许多人沮丧的是，这些干预措施往往无法改变所研究的途径的比率。 这些失败导致人们越来越认识到，途径通量的“控制”分布在代谢途径的许多酶中，并且可以根据条件从酶到酶而变化。 代谢控制理论预测控制在途径的许多酶中的分布（Veech，R.L.和Fell，D.A. Cell Biochem.& Function 14：229-236，1996）。 然而，实际证明和测试这些理论在技术上是困难的。 我们是第一个对每个步骤的通量、动力学和热力学常数以及对主要代谢途径中的通量控制进行正式分析所需的所有底物和产物的水平进行所需测量的实验室（Kashiwaya，Y.等人，J.Biol.Chem.269：25502-25514，1994）。 我们继续表明酮体可以在心脏中起作用以克服心脏中的胰岛素抗性（Kashiwaya，J. 80：50A 64A，1997）。 自从Kashiwaya博士离开这个实验室后，我继续与他合作，他与日本约纳戈鸟取大学神经学系的其他人一起，应用我们以前工作中的这些见解来研究酮体对两种最常见的退行性神经疾病的两种神经元培养模型的影响。 通过向胚胎大鼠海马神经元培养物中加入淀粉样蛋白β 1-42来模拟阿尔茨海默病，通过向中脑神经元培养物中加入MPP+来模拟帕金森病。 在这两种情况下，酮体保护神经元免受这些非常不同的毒素引起的死亡。 酮体在这些条件下保护神经元的能力提供了治疗这些非常常见的疾病以及由糖酵解或线粒体能量产生失败引起的其他疾病的可能性。 这项工作现已出现在：Kashiwaya，Y.，Takeshima，T.，Mori，N.，Nakashima，K.，美国，Clarke，K.，Veech，R.L. Proc. Natl. Acad. Sci. (USA)97：5440-5444，2000. 2000年5月3日，在美国国立卫生研究院举行的罕见病会议上，讨论了酮体在治疗神经系统疾病（包括难治性癫痫和胰岛素抵抗，如小妖精病）中的应用。 代谢控制方面的工作是与巴塞罗那大学生物化学系和加州大学洛杉矶分校海港研究所合作完成的，今年针对的是磷酸己糖途径和硫胺素在某些癌症中的作用，并发表在Cascante，M.，Centelles，J.J.，Veech，R.L.，Lee，W-N.P.，Boros，L.G.营养与癌症36：150-154，2000。

It is widely believed that the steps in the major metabolic pathways are known and that the control of flux through these pathways occurs at a very limited number of "rate limiting" steps. This concept has lead to the design of drugs to alter the kinetics of these "rate limiting enzymes". It has also led to attempts to alter metabolic pathways by altering the amounts of rate limiting enzymes using the techniques of molecular biology. To the dismay of many, such interventions often fail to alter the rates of the pathways under study. These failures have led to an increased awareness that "control" of pathway flux is distributed among many enzymes of a metabolic pathway and can vary from enzyme to enzyme depending upon conditions. Metabolic control theory predicts distribution of control among many enzymes of a pathway (Veech, R.L. & Fell, D.A. Cell Biochem. & Function 14: 229-236, 1996). However, actual demonstration and testing of such theories was technically difficult. We were the first laboratory to make the required measurements of flux, kinetic and thermodynamic constants of each step, and the levels of all substrates and products required to make such a formal analysis of flux control in a major metabolic pathway (Kashiwaya, Y. et al, J. Biol. Chem. 269: 25502-25514, 1994). We went on to show that ketone bodies can act in heart to overcome insulin resistance in heart (Kashiwaya, J. et al, Am J. Cardiol. 80: 50A 64A, 1997). Since Dr. Kashiwaya left this laboratory, I have continued to collaborate with him and he, with others at the Department of Neurology of Tottori University in Yonago, Japan, have applied these insights from our previous work to investigate the effects of ketone bodies upon two neuronal culture models of the two most common degenerative neurological diseases. Alzheimer's disease was modeled by adding amyloid beta 1-42 to embryonic rat hippocampal neuronal cultures and Parkinson's disease was modeled by adding MPP+ to mesencephalic neuronal cultures. In both case, ketone bodies protected neurons from death induced by these very different toxins. The ability of ketone bodies to protects neurons under these conditions offers the possibility of therapy of these very common diseases as well as other diseases resulting from failures in either glycolysis or mitochondrial energy generation. This work has now appeared in: Kashiwaya,Y., Takeshima,T., Mori,N., Nakashima,K., Clarke,K., Veech,R.L. Proc. Natl. Acad. Sci. (USA) 97: 5440-5444, 2000. Discussions of the uses of ketone bodies in the treatment of neurological diseases including refractory epilepsy and insulin resistance such as Leprechaunism was held in a Rare Disease Meeting at NIH on May 3, 2000. Work on metabolic control was done in collaboration with the Dept of Biochemistry, U of Barcelona and the Harbor UCLA Research Institute and was directed this year toward the hexosemonophosphate pathway and the role of thiamine in certain cancers and appeared in Cascante,M., Centelles,J.J., Veech, R.L., Lee, W-N.P., Boros, L.G. Nutrition and Cancer 36: 150-154, 2000.