血浆中的维生素B12</sub>与转钴胺素蛋白（transcobalamin，TC）Ⅰ、Ⅱ、Ⅲ结合，其中TCⅡ尤为重要。
B-bod I-bod O O B-dru I-dru I-dru I-dru I-dru I-dru O O O O O O O B-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod I-bod O O O O O B-bod I-bod I-bod O O O O O