HEXOKINASE AND ENERGY METABOLISM IN THE BRAIN

脑己糖激酶可逆地与外线粒体结合，与 酶在结合形式和溶解形式之间的相对分布 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)。此分布对 细胞内葡萄糖代谢状态，结合比例增加 糖酵解活性增强期间发现的酶。变化中的 细胞内分布被认为代表了一种调节 催化活性，结合形式的酶比 溶解了。 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开发出来，并基于 根据初步观察，可能允许估计可溶颗粒物 己糖激酶在单个细胞中的分布。如上所述，由于这一点 分布对相对糖酵解率很敏感，能量状态 单个细胞可以用这种方法进行评估。的第二个目标 拟议的工作将是阐明特定的分子基础 己糖激酶与线粒体膜的相互作用。一个 已从外线粒体中纯化出己糖激酶结合蛋白 薄膜。初步研究还表明，它是N-末端 酶的一个区域，主要参与与 薄膜。己糖激酶结合的化学和物理特性 蛋白质和N端的酶序列可能会提供更详细的 了解这一具体认可和约束的基础。

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.