Nicolas J P, Guéant J L
INSERM 308, Biochimie Nutritionnelle, Faculté de Médecine, Vandoeuvre-les-Nancy.
Bull Acad Natl Med. 1992 Mar;176(3):327-40; discussion 341-3.
Since the existence of vitamin B12 was suggested by Castle in the first few decades of this century, vitamin B12 has been the subject of many studies which have proved the high complexity of it assimilation by the organism. Over the last few years the marked progress in functional digestive exploration methods and the physical and the chemical characteristics of biological molecules have revived the established idea of the vitamin's intraluminal transit. Our recent studies have been concentrated on the bilioduodenopancreatic stage of the vitamin B12 transport. In nature, vitamin B12 is only exceptionally met in its free form it is always associated with a binder. Like a ball being tossed from one player to another, it moves between binders. Alimentary vitamin B12 released from its protein complexes by culinary preparation and gastric secretions, is combined with haptocorrin. Around the duodenum the transfer of B12 on intrinsic factor is due to partial degradation of haptocorrin by pancreatic enzymes and intraluminal pH balance. This combined with intrinsic factor the vitamin can be caught by the ileal receptor. The partial degradation haptocorrin joins vitamin B12 analogs from excreted bile or synthesized by the intestinal microorganisms.
自本世纪头几十年卡斯尔提出维生素B12的存在以来，维生素B12一直是众多研究的主题，这些研究证明了机体对其吸收过程的高度复杂性。在过去几年中，功能性消化探索方法以及生物分子的物理和化学特性方面取得的显著进展，使人们重新关注维生素在管腔内转运的既定观点。我们最近的研究集中在维生素B12转运的胆胰十二指肠阶段。在自然界中，维生素B12仅以游离形式偶尔出现，它总是与一种结合剂结合。就像一个球从一个球员传给另一个球员一样，它在结合剂之间移动。通过烹饪制备和胃分泌物从其蛋白质复合物中释放出来的膳食维生素B12，与运钴胺素结合。在十二指肠周围，维生素B12向内因子的转移是由于运钴胺素被胰酶部分降解以及管腔内pH平衡所致。这种与内因子结合的维生素能够被回肠受体捕获。部分降解的运钴胺素与来自排泄胆汁或由肠道微生物合成的维生素B12类似物结合。
