Callahan J W, Khalil M
Pediatr Res. 1975 Dec;9(12):914-8. doi: 10.1203/00006450-197512000-00010.
Sphingomyelinase was effectively extracted cultured fibroblasts homogenized in 1% glycine. The average specific activity was 24.6 nmol substrate hydrolyzed per hr per mg protein. Cultured cells from two cases of Niemann-Pick disease type A and one case of type B had markedly reduced enzyme activity, whereas, in type E cells, total activity was twice normal. Sphingomyelinase was resolved by isoelectric focusing into three peaks of activity (I-II), where I and II were the major forms. Species I had a pI of 4.6, II a pI of 4.8, and III a pI of 5.0. All three peaks, although markedly reduced, were present in cell extracts from both types A and B. All species of enzyme in B cells were found at higher levels than in A cells. Cultured cells from a case of type E contained sphingomyelinase I at a level several fold higher than normal, species II was absent, whereas III was found at near normal levels.
鞘磷脂酶是从在1%甘氨酸中匀浆的培养成纤维细胞中有效提取的。平均比活性为每小时每毫克蛋白质水解24.6纳摩尔底物。两例A型尼曼-匹克病和一例B型尼曼-匹克病的培养细胞酶活性明显降低，而E型细胞的总活性是正常的两倍。通过等电聚焦将鞘磷脂酶分离为三个活性峰（I-II），其中I和II是主要形式。I型的pI为4.6，II型的pI为4.8，III型的pI为5.0。所有三个峰虽然明显降低，但在A型和B型细胞提取物中均存在。B细胞中所有酶种类的水平均高于A细胞。一例E型病例的培养细胞中鞘磷脂酶I的水平比正常水平高几倍，不存在II型，而III型的水平接近正常。
