University of Groningen, Faculty of Science and Engineering, Groningen Biomolecular Sciences and Biotechnology, Membrane Enzymology Group, Groningen, Netherlands.
University of Groningen, Faculty of Science and Engineering, Groningen Biomolecular Sciences and Biotechnology, Membrane Enzymology Group, Groningen, Netherlands.
Vitam Horm. 2022;119:121-148. doi: 10.1016/bs.vh.2022.01.008. Epub 2022 Mar 7.
A wide variety of organisms encode cobalamin-dependent enzymes catalyzing essential metabolic reactions, but the cofactor cobalamin (vitamin B12) is only synthesized by a subset of bacteria and archaea. The biosynthesis of cobalamin is complex and energetically costly, making cobalamin variants and precursors metabolically valuable. Auxotrophs for these molecules have evolved uptake mechanisms to compensate for the lack of a synthesis pathway. Bacterial transport of cobalamin involves the passage over one or two lipidic membranes in Gram-positive and -negative bacteria, respectively. In higher eukaryotes, a complex system of carriers, receptors and transporters facilitates the delivery of the essential molecule to the tissues. Biochemical and genetic approaches have identified different transporter families involved in cobalamin transport. The majority of the characterized cobalamin transporters are active transport systems that belong to the ATP-binding cassette (ABC) superfamily of transporters. In this chapter, we describe the different cobalamin transport systems characterized to date that are present in bacteria and humans, as well as yet-to-be-identified transporters.
许多生物体编码钴胺素依赖的酶，催化重要的代谢反应，但钴胺素（维生素 B12）的辅因子仅由一部分细菌和古菌合成。钴胺素的生物合成非常复杂且耗费能量，因此钴胺素变体和前体在新陈代谢中具有很高的价值。这些分子的营养缺陷型已经进化出摄取机制来弥补缺乏合成途径的问题。细菌对钴胺素的运输分别涉及革兰氏阳性菌和革兰氏阴性菌中一个或两个脂膜的穿过。在高等真核生物中，一个复杂的载体、受体和转运蛋白系统有助于将必需的分子递送到组织中。生化和遗传方法已经确定了不同的转运蛋白家族参与钴胺素的运输。大多数已鉴定的钴胺素转运蛋白是属于 ATP 结合盒（ABC）转运蛋白超家族的主动运输系统。在这一章中，我们描述了迄今为止在细菌和人类中发现的不同的钴胺素转运系统，以及尚未确定的转运蛋白。
