Department of Agricultural, Life and Environmental Sciences, Faculty of Agriculture, Tottori University, Tottori 680-8553, Japan.
Division of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
Molecules. 2020 Jul 17;25(14):3268. doi: 10.3390/molecules25143268.
Adenyl cobamide (commonly known as pseudovitamin B) is synthesized by intestinal bacteria or ingested from edible cyanobacteria. The effect of pseudovitamin B on the activities of cobalamin-dependent enzymes in mammalian cells has not been studied well. This study was conducted to investigate the effects of pseudovitamin B on the activities of the mammalian vitamin B-dependent enzymes methionine synthase and methylmalonyl-CoA mutase in cultured mammalian COS-7 cells to determine whether pseudovitamin B functions as an inhibitor or a cofactor of these enzymes. Although the hydoroxo form of pseudovitamin B functions as a coenzyme for methionine synthase in cultured cells, pseudovitamin B does not activate the translation of methionine synthase, unlike the hydroxo form of vitamin B does. In the second enzymatic reaction, the adenosyl form of pseudovitamin B did not function as a coenzyme or an inhibitor of methylmalonyl-CoA mutase. Experiments on the cellular uptake were conducted with human transcobalamin II and suggested that treatment with a substantial amount of pseudovitamin B might inhibit transcobalamin II-mediated absorption of a physiological trace concentration of vitamin B present in the medium.
腺嘌呤钴胺素（通常称为假维生素 B）由肠道细菌合成或从可食用的蓝细菌中摄取。假维生素 B 对哺乳动物细胞中钴胺素依赖性酶活性的影响尚未得到很好的研究。本研究旨在研究假维生素 B 对培养的哺乳动物 COS-7 细胞中依赖维生素 B 的酶蛋氨酸合成酶和甲基丙二酰辅酶 A 变位酶活性的影响，以确定假维生素 B 是否作为这些酶的抑制剂或辅助因子起作用。尽管假维生素 B 的羟肟形式在培养细胞中作为蛋氨酸合成酶的辅酶起作用，但它不像维生素 B 的羟肟形式那样激活蛋氨酸合成酶的翻译。在第二个酶反应中，假维生素 B 的腺嘌呤形式不作为甲基丙二酰辅酶 A 变位酶的辅酶或抑制剂起作用。用人类转钴胺素 II 进行的细胞摄取实验表明，用大量的假维生素 B 处理可能会抑制转钴胺素 II 介导的对培养基中存在的生理痕量浓度的维生素 B 的吸收。
