Pezacka E H, Jacobsen D W, Luce K, Green R
Department of Laboratory Hematology, Cleveland Clinic Foundation, Ohio 44195.
Biochem Biophys Res Commun. 1992 Apr 30;184(2):832-9. doi: 10.1016/0006-291x(92)90665-8.
The conversion of cyanocobalamin to adenosyl- and methylcobalamin is impaired in cobalamin-deficient cultured human glial cells. In contrast cultured human skin fibroblasts retained their ability to synthesize coenzyme forms when grown in cobalamin-deficient medium. Cells were pre-conditioned by growing in cobalamin-deficient media for six weeks and then subcultured in medium containing either free or transcobalamin II-bound 57Co-cyanocobalamin. Although both coenzyme levels were low in cobalamin-deficient glial cells, the decrease in methylcobalamin was more marked than that of adenosylcobalamin. Methionine synthase and Cb1 reductase activities were markedly decreased in cobalamin-deficient glial cells but were unchanged in fibroblasts cultured in cobalamin-deficient medium. Our data suggest that in glial cells, cobalamin coenzyme synthesis and function is exquisitely sensitive to short-term cobalamin deprivation. Glial cells apparently synthesize and secrete transcobalamin II since antibodies directed against the transport protein inhibit the uptake of free cobalamin.
在钴胺素缺乏的培养人神经胶质细胞中，氰钴胺向腺苷钴胺素和甲基钴胺素的转化受损。相比之下，培养的人皮肤成纤维细胞在钴胺素缺乏的培养基中生长时，仍保留合成辅酶形式的能力。细胞先在钴胺素缺乏的培养基中培养六周进行预处理，然后在含有游离或与转钴胺素II结合的57Co-氰钴胺素的培养基中传代培养。尽管钴胺素缺乏的神经胶质细胞中两种辅酶水平都很低，但甲基钴胺素的下降比腺苷钴胺素更明显。钴胺素缺乏的神经胶质细胞中蛋氨酸合酶和Cb1还原酶活性显著降低，但在钴胺素缺乏的培养基中培养的成纤维细胞中则没有变化。我们的数据表明，在神经胶质细胞中，钴胺素辅酶的合成和功能对短期钴胺素缺乏极为敏感。神经胶质细胞显然合成并分泌转钴胺素II，因为针对转运蛋白的抗体可抑制游离钴胺素的摄取。
