Molecular basis of lysosomal storage disease and the possibility of a new therapeutic approach

(1)人α-半乳糖苷酶的组织特异性翻译后修饰研究了人α-半乳糖苷酶（α-Gal）转基因小鼠的基因表达和翻译后糖基化。小鼠的心脏和肝脏表达大量的转录本以及高α-Gal活性。心脏和肾脏中的基因产物对内切糖苷酶H消化敏感，而脾脏和肝脏中的基因产物对内切糖苷酶H消化有很大的抗性。糖肽酶F处理证实了酶的肽部分的相同分子量。我们的结论是，基因产物的异质性分子量是由不同程度的翻译后糖基化在小鼠组织。(2)Morquio B病患者突变β-半乳糖苷酶的底物特异性改变β-半乳糖苷脂沉积症是一种由酸性β-半乳糖苷酶（β-Gal）缺乏引起的溶酶体贮积病，包括两种不同的临床表型，GM 1-神经节苷脂沉积症和Morquio B病。不 ...更多信息 前者有中枢神经系统病变，而后者有骨骼病变而无中枢神经系统病变。为了阐明两种疾病之间临床差异的分子证据，我们使用人工底物类似物研究了来自GM 1-神经节苷脂沉积症和Morquio B病患者的突变β-Gal的底物特异性。Morquio B病的突变型β-Gal（W237 L/W237 L，Y83 H/R482 C）与硫酸角质素类似物Gal β 1 -4Glc NAc的亲和力低于GM 1-神经节苷脂类似物Galβ1-3GalNAc，但正常β-Gal和GM 1-神经节苷脂病的突变型β-Gal（R201 C/R201 C，151 T/151 T）的亲和力无明显差异。此外，Morquio B突变体对类似物（Galβ1-4GlcNAc/Galβ1-3GalNAc）的水解率显著降低，而GM 1-神经节苷脂沉积症突变体对正常β-Gal的水解率相似。我们的结论是，不同的临床表型GM 1神经节苷脂沉积症和莫基奥B病是由改变底物特异性的突变体P-Gal与莫基奥B病患者的独特基因突变。少

(1) Tissue-specific posttranslational modification of human α-galactosidaseHeterogeneous gene expression and posttranslational glycosylation were examined in human α-galactosidase (α-Gal) transgenic mouse. The heart and liver of the mouse expressed a high amount of transcript as well as high α-Gal activity. Its gene products in the heart and kidney were sensitive to endoglycosidase H digestion, but those in the spleen and liver were largely resistant. Glycopeptidase F treatment confirmed an identical molecular mass for the peptide moiety of the enzyme. We conclude that heterogeneous molecular mass of the gene products is caused by different degree of posttranslational glycosylation in murine tissues.(2) Altered substrate specificity of mutant β-galactosidase in patients with Morquio B diseaseβ-Galactosidodosis is a lysosomal storage disease caused by a deficiency of acid β-galactosidase (β-Gal) consisting of two different clinical phenotypes, GM1-gangliosidosis and Morquio B disease. T … More he former has central nervous system lesions, whereas the latter has skeletal lesions with no central nervous system lesions. To clarify the molecular evidence to account for clinical difference between both diseases, we investigated substrate specificity of mutant β-Gal derived from patients with GM1-gangliosidosis and Morquio B disease using artificial substrate analogs. Mutant β-Gal (W237L/W237L, Y83H/R482C) from Morquio B disease exhibited relatively low affinity to Galβl-4Glc NAc , an analog of keratan sulfate, as compared with Galβ1-3GalNAc, an analog of GM1-gangliosid, but there was not such difference in both normal β-Gal and mutant β-Gal (R201C/R201C, 151T/151T) from GM1-gangliosidosis. Furthermore, Morquio B mutants showed considerable decrease in hydrolysis ratio for the analogs (Galβ1-4GlcNAc/Galβ1-3GalNAc), yet GM1-gangliosidosis mutants had similar hydrolysis ratio to normal β-Gal. We conclude that distinct clinical phenotypes between GM1-gangliosidosis and Moquio B disease are caused by altered substrate specificity of mutant P-Gal resulting from unique gene mutations in patients with Morquio B disease. Less