Douglas T C, Kimmel K A, Dawson P E
Genetics. 1982 Mar;100(3):455-73. doi: 10.1093/genetics/100.3.455.
Two genetically variant forms of rat "acid" beta-galactosidase were found to differ in isoelectric point and pH dependence, but not in thermostability or sensitivity to inhibition by p-mercuribenzoate (PMB). The results of two backcrosses and an intercross indicated that the isoelectric focusing phenotypes are controlled by two codominant alleles at a single autosomal locus, for which we propose the name Glb-1. No significant linkage between Glb-1 and albino (LG I), brown (LG II), or hooded (LG VI) was observed. Strain-specific differences in total levels of kidney beta-galactosidase were detected, but it is not yet known whether the variation is controlled by genes linked to Glb-1. Experiments in which organ homogenates were incubated with neuraminidase indicated that the genetically variant forms do not result from differences in sialylation, though sialylation does appear to be largely responsible for the presence of multiple bands within each phenotype and for differences in the banding patterns of beta-galactosidases derived from different organs. The beta-galactosidase present in the bands used for Glb-1 typing resembles human GM1 gangliosidase (GLB1) with respect to pH optimum, substrate specificity, and susceptibility to inhibition by PMB. It also appears that Glb-1 is homologous with the Bgl-e locus of the mouse. In rats as in mice the genetically variant bands of beta-galactosidase are active at acid pH and have relatively high isoelectric points. In both species these bands are readily detectable in kidney homogenates, and can be revealed in homogenates of liver or spleen following treatment with neuraminidase. The presence of the same beta-galactosidase bands in homogenates of rat kidney and small intestine as well as in neuraminidase-treated homogenates of liver and spleen suggests that the Glb-1 variants differ by one or more point mutations in the structural gene for "acid" beta-galactosidase.
已发现大鼠“酸性”β-半乳糖苷酶的两种基因变异形式在等电点和pH依赖性方面存在差异，但在热稳定性或对对氯汞苯甲酸（PMB）抑制的敏感性方面无差异。两次回交和一次杂交的结果表明，等电聚焦表型由位于单个常染色体位点的两个共显性等位基因控制，我们为此提议命名为Glb-1。未观察到Glb-1与白化（LG I）、棕色（LG II）或头巾色（LG VI）之间有显著连锁。检测到肾脏β-半乳糖苷酶总水平存在品系特异性差异，但尚不清楚这种变异是否由与Glb-1连锁的基因控制。用神经氨酸酶孵育器官匀浆的实验表明，基因变异形式并非由唾液酸化差异导致，尽管唾液酸化似乎在很大程度上导致了每种表型内多条带的出现以及不同器官来源的β-半乳糖苷酶条带模式的差异。用于Glb-1分型的条带中存在的β-半乳糖苷酶在最适pH、底物特异性和对PMB抑制的敏感性方面类似于人类GM1神经节苷脂酶（GLB1）。似乎Glb-1也与小鼠的Bgl-e位点同源。在大鼠中，如同在小鼠中一样，β-半乳糖苷酶的基因变异条带在酸性pH下具有活性且等电点相对较高。在这两个物种中，这些条带在肾脏匀浆中很容易检测到，在用神经氨酸酶处理后，在肝脏或脾脏匀浆中也可显现。大鼠肾脏和小肠匀浆以及经神经氨酸酶处理的肝脏和脾脏匀浆中存在相同的β-半乳糖苷酶条带，这表明Glb-1变异体在“酸性”β-半乳糖苷酶结构基因中存在一个或多个点突变。
