STRUCTURE AND FUNCTION OF B12-BINDING PROTEINS

其目的是阐明其结构和功能特性 钴胺(CB1，维生素B12)结合蛋白，参与 细胞对CB1的摄取和利用，并将此信息应用于 临床情况的数量。 我们将研究观察到的CB1的功能意义 优先与胃液中的R蛋白结合，不转移 直到R蛋白部分被部分降解后的内源性因子 通过小肠中的胰酶。我们将进一步定义 内源性因子和转钴胺II在大鼠回肠吸收中的作用 并研究CB1释放的本质上未明确的机制 从细胞中释放，特别强调从回肠吸收中释放 细胞和肝细胞。 我们将研究哺乳动物CB1依赖的两种酶的调节， L-甲基丙二酰辅酶A变位酶和蛋氨酸合成酶，并阐明了 CB1向辅酶Ado-CB1转化的途径 和CH3-CB1。我们将研究甲基丙二酸的代谢和 调查它是否有一个重要而被忽视的 生化功能。 我们将进一步定义回肠和中性粒细胞-肝细胞的机制 防止潜在的肠道吸收和组织传播 细菌来源的有毒CB1类似物并确定这些CB1 在各种疾病中，血液和组织中都存在类似物。我们会 研究一类新的CB1类似物的性质和起源 最近在人和动物的血液和组织中观察到 复合维生素-矿物质药丸和动物咀嚼，以及暴露于 一氧化二氮。我们将测定其生物活性和抑制力。 各种CB1类似物的性质，用它们来培育动物 CB1缺乏症模型的建立及其化疗活性的研究 抗肿瘤细胞的药物。 甲基丙二酸、同型半胱氨酸和蛋氨酸将在不同的 基于毛细管气相色谱-质谱法的血液样品 光谱分析。这些检测使这两种哺乳动物的活动 CB1依赖的酶将在体内进行评估，并将用于 涉及显著和轻度CB1缺乏症患者的研究，各种 血清CB1水平、各种神经精神疾病和受试者 在工作场所暴露于一氧化二氮。

The objectives are to elucidate the structural and functional properties of cobalamin (Cb1, vitamin B12)-binding proteins which are involved in the cellular uptake and utilization of Cb1, and to apply this information to a number of clinical situations. We will study the functional significance of the observation that Cb1 is preferentially bound by R protein in gastric juice and is not transferred to instrinsic factor until after the R protein moiety is partially degraded by pancreatic enzymes in the small intestine. We will further define the role of intrinsic factor and transcobalamin II in the ileal absorption of Cb1 and study the essentially undefined mechanisms by which Cb1 is released from cells, with particular emphasis on its release from ileal absorptive cells and hepatocytes. We will study the regulation of the two mammalian Cb1-dependent enzymes, L-methylmalonyl-CoA mutase and methionine synthetase, and elucidate the pathways involved in the conversion of Cb1 to its coenzyme forms, Ado-Cb1 and CH3-Cb1. We will study the metabolism of methylmalonic acid and investigate the possibility that it has an important and overlooked biochemical function. We will further define the ileal and neutrophil-hepatocyte mechanisms that prevent the intestinal absorption and tissue dissemination of potentially toxic Cb1 analogues of bacterial origin and determine if these Cb1 analogues are present in blood and tissues in various diseases. We will study the properties and origins of a new class of Cb1 analogues that have recently been observed in human and animal blood and tissues, in multivitamin-mineral pills and animal chows, and in animals exposed to nitrous oxide. We will determine the biologic activities and inhibitory properties of a variety of Cb1 analogues, use them to develop an animal model of Cb1 deficiency, and investigate their activity as chemotherapeutic agents against malignant cells. Methylmalonic acid, homocysteine, and methionine will be assayed in various blood samples using assays based on capillary gas chromatography-mass spectrometry. These assays enable the activities of the two mammalian Cb1-dependent enzymes to be assessed in vivo and will be utilized in studies involving patients with marked and mild Cb1 deficiency, various levels of serum Cb1, various neuropsychiatric diseases, and subjects exposed to nitrous oxide in the work place.