HEXOKINASE AND ENERGY METABOLISM IN THE BRAIN

脑己糖激酶可逆地结合到线粒体外膜， 酶在结合形式和溶解形式之间的相对分布是 由特定代谢物（葡萄糖6-磷酸）的细胞浓度控制 可能是最有影响力的）。 该分布对 细胞中葡萄糖代谢的状态，结合比例增加 在糖酵解活动增加期间发现的酶。 变化 细胞内分布被认为代表了调节 催化活性，酶的结合形式比酶的结合形式更有活性。 溶解。 拟议的工作将侧重于这一现象的两个主要方面。 第一、 免疫组织化学电子显微镜方法已经发展， 根据初步观察，可以估计可溶性颗粒 己糖激酶在单个细胞中的分布。 如上所述，由于 分布是敏感的相对糖酵解速率，能量状态， 可以通过该方法评估单个细胞。 的第二个目的 建议的工作将是阐明具体的分子基础， 己糖激酶和线粒体外膜之间的相互作用。 一 己糖激酶结合蛋白已经从线粒体外膜中纯化出来， 膜的 初步研究还表明，它是N-末端 酶的主要参与与蛋白质相互作用的区域 膜的 己糖激酶结合的化学和物理表征 蛋白质和酶的N-末端序列可以提供更详细的 理解这种具体承认和约束的基础。

Brain hexokinase binds reversibly to the outer mitochondial membrane, with the relative distribution of the enzyme between bound and solubilized forms being governed by cellular concentrations of specific metabolites (glucose 6-phosphate probably being the most influential). This distribution is sensitive to the status of glucose metabolism in the cells, with increased proportions of bound enzyme found during periods of increased glycolytic activity. Variation in intracellular distribution is thought to represent a mechanims for regulation of catalytic activity, with the bound form of the enzyme being more active than the solubilized. The proposed work will focus on two major aspects of this phenomenon. First, immunohistochemical electron microscopic methods have been developed and, based on preliminary observations, may permit estimation of the soluble-particulate distribution of hexokinase in individual cells. Since, as noted above, this distribution is sensitive to relative glycolytic rate, the energy status in individual cells may be assessed by this method. A second objective of the proposed work will be to elucidate the molecular basis for the specific interaction between hexokinase and the outer mitochondrial membrane. A hexokinase-binding protein has been purified from the outer mitochondrial membrane. Preliminary studies have also suggested that it is the N-terminal region of the enzyme that is primarily involved in interaction with the membrane. Chemical and physical characterization of the hexokinase-binding protein and the N-terminal sequence of the enzyme may provide a more detailed understanding of the basis for this specific recognition and binding.