Mahoney M J, Hart A C, Steen V D, Rosenberg L E
Proc Natl Acad Sci U S A. 1975 Jul;72(7):2799-803. doi: 10.1073/pnas.72.7.2799.
We measured the synthesis of 5'-deoxyadenosylcobalamin (AdoCbl) in fibroblast extracts from patients with inherited methylmalonicacidemia due to deficient activity of the cobalamin-dependent holoenzyme, methylmalonyl-CoA mutase (EC 5.4.99.2). Previous studies with intact fibroblasts from patients whose holoenzyme deficiency was secondary to abnormal cobalamin metabolism had defined two phenotypes, one in which whole cells failed to accumulate AdoCbl and a second in which they failed to accumulate both AdoCbl and the second cobalamin coenzyme, methylcobalamin. With a broken cell assay of AdoCbl synthesis in cell extracts and the cell lines are named cbl A mutants; the other class shows severe deficiency of AdoCbl synthesis and the cell lines are named cbl B mutants. We define cbl C mutants as those in which both AdoCbl and methylcobalamin fail to accumulate in intact cells. The assay for AdoCbl synthesis is thought to measure two enzymatic activities, cob(II)alamin reductase (EC 1.6.99.9) and cob(I)alamin adenosyltransferase (EC 2.5.1.17). Subcellular fractionation studies place this combined activity in mitochondria.
我们检测了因钴胺素依赖性全酶甲基丙二酰辅酶A变位酶（EC 5.4.99.2）活性不足而患有遗传性甲基丙二酸血症患者的成纤维细胞提取物中5'-脱氧腺苷钴胺素（AdoCbl）的合成情况。先前对全酶缺乏继发于异常钴胺素代谢的患者的完整成纤维细胞进行的研究确定了两种表型，一种是全细胞无法积累AdoCbl，另一种是全细胞无法积累AdoCbl和第二种钴胺素辅酶甲基钴胺素。通过细胞提取物中AdoCbl合成的破碎细胞测定法，这些细胞系被命名为cbl A突变体；另一类显示AdoCbl合成严重不足，这些细胞系被命名为cbl B突变体。我们将cbl C突变体定义为完整细胞中AdoCbl和甲基钴胺素均无法积累的那些突变体。AdoCbl合成测定法被认为可测量两种酶活性，即钴胺素（II）还原酶（EC 1.6.99.9）和钴胺素（I）腺苷转移酶（EC 2.5.1.17）。亚细胞分级分离研究表明这种联合活性存在于线粒体中。
