STRUCTURAL STUDIES ON COBALAMINS

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 类柯瑞酸依赖性酶广泛存在于自然界中，在人类、动物和微生物的代谢中起着关键作用。人体中存在两种已知的B12依赖性酶：甲基钴胺素（MeCbl）依赖性甲硫氨酸合酶和腺苷钴胺素（Adenosylbobalamin）依赖性甲基丙二酰辅酶A β。B12缺乏的临床标志是巨幼细胞性贫血（恶性贫血）和/或神经病。在到达细胞后，钴胺素衍生物通过目前不明确的机制转化为MeCbl和MeCbl。在过去几十年中进行了许多研究，涉及从哺乳动物细胞、组织和血液以及食物和海藻等其他生物样品中提取和鉴定钴矿。腺苷钴胺素、甲基钴胺素和水钴胺素是从生物样品中分离的主要钴胺素代谢物，但也有报道称从生物来源中分离出硝基钴胺素和硫维生素钴胺素，以及沿着其他未知的复合物。 我们已经合成了一些钴胺素衍生物，以协助鉴定从生物样品中分离的未知钴胺素，我们已经确定了一些这些复合物的晶体结构，包括N-乙酰半胱氨酰钴胺素，亚硝基钴胺素和水钴胺素在原子分辨率（< 0.8 <$）使用高能X射线（> 15000 eV）和非常短的晶体检测器距离。 SSRL收集的数据与使用传统方法（通常使用Mo-Ka辐射）收集的数据相当，在某些情况下更好。

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 and aquocobalamin at atomic resolution (< 0.8 ¿) using high energy X-rays (> 15000 eV) and very short crystal-detector distances. The data collected at SSRL is comparable to, and in some cases better than the data collected using conventional methods (which generally employ Mo-Kalpha radiation).