STRUCTURAL STUDIES ON COBALAMIN COMPLEXES

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 类固醇依赖的酶在自然界中广泛存在，在人类、动物和微生物代谢中发挥着关键作用。人类存在两种已知的依赖于B12的酶：依赖于甲钴胺(MeCbl)的蛋氨酸合成酶和依赖于腺苷钴胺(ADOCbl)的甲基丙二酰辅酶A变位酶。B12缺乏的临床特征是巨幼细胞性贫血(恶性贫血)和/或神经性疾病。在到达细胞后，钴胺衍生物通过目前定义不清的机制转化为MeCbl和Adobe Cbl。在过去的几十年里，除了食物和海藻等其他生物样本外，还进行了许多研究，涉及从哺乳动物细胞、组织和血液中提取和鉴定钴蛋白。腺苷钴胺、甲钴胺和水钴胺是从生物样品中分离得到的主要钴胺代谢物，但也有报道从生物来源中分离出硝酸钴胺和硫钴胺，以及其他未知的络合物。我们合成了一些钴胺衍生物来帮助从生物样品中分离出未知的钴胺类化合物，并利用高能X射线(高于15keV)和很短的晶体探测器距离在原子分辨率(&lt；0.8A)下测定了其中一些配合物的晶体结构，包括N-乙酰半胱氨酸钴胺、亚硝酸钴胺、水钴胺、乙基钴胺、丁基钴胺和最近的谷硫酰钴胺。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Corrinoid-dependent enzymes are widespread in nature and play key roles in human, animal and microbial metabolism. Two known B12-dependent enzymes exist in humans: methylcobalamin (MeCbl)-dependent methionine synthase and adenosylcobalamin (AdoCbl)-dependent methylmalonyl-coenzyme A mutase. The clinical hallmarks of B12 deficiency are megaloblastic anemia (?pernicious anemia?), and/or neuropathies. Upon reaching cells, cobalamin derivatives are converted to MeCbl and AdoCbl by currently ill-defined mechanisms. Many studies have been carried out over the past several decades involving the extraction and identification of cobalamins from mammalian cells, tissue and blood, in addition to other biological samples such as foods and seaweed. Adenosylcobalamin, methylcobalamin and aquacobalamin are the major cobalamin metabolites isolated from biological samples but there are also reports of the isolation of nitrocobalamin and sulfitocobalamin from biological sources, along with other unknown complexes. We have synthesized a number of cobalamin derivatives to assist in the identification of unknown cobalamins isolated from biological samples, and we have determined the crystal structures of a number of these complexes including N-acetylcysteinylcobalamin, nitrosocobalamin, aquocobalamin, ethyelcobalamin, butylcobalamin and more recently glutathionylcobalamin all at atomic resolution (< 0.8 A) using high energy x-rays (above 15 keV) and very short crystal-detector distances.