MOLECULAR DEFECT IN COMBINED BETA-GALACTOSIDASE AND NEURAMINIDASE DEFICIENCY IN MAN
MOLECULAR DEFECT IN COMBINED BETA-GALACTOSIDASE AND NEURAMINIDASE DEFICIENCY IN MAN
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DOI：
10.1073/pnas.79.15.4535
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发表时间：
1982-01-01
期刊：
影响因子：
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通讯作者：
GALJAARD, H
中科院分区：
文献类型：
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作者：
DAZZO, A;HOOGEVEEN, A;GALJAARD, H
在正常人成纤维细胞中，β-半乳糖苷酶的酶活性85，000-道尔顿前体形式半乳糖苷酶通过许多中间体被加工成成熟的64，000-道尔顿形式。此外，还有一种无酶活性的32，000-道尔顿组分及其54，000-道尔顿前体。在来自患有β-CD综合缺陷的患者的成纤维细胞中，半乳糖苷酶和神经氨酸酶这最后两种组分不存在，并且几乎没有任何成熟的β-半乳糖苷酶可以证明。然而，在突变的成纤维细胞中，前体β-半乳糖苷酶正常合成和加工。过度的溶酶体内降解是导致成熟β-淀粉样蛋白缺乏的原因。半乳糖苷酶可通过加入蛋白酶抑制剂亮抑酶肽（leupeptin）而部分校正，这导致85，000-道尔顿前体β-半乳糖苷酶的积累。半乳糖苷酶和部分加工的66，00-道尔顿形式。当突变体细胞在存在从NH 4Cl刺激的细胞培养物的培养基中纯化的校正因子的情况下生长时，半乳糖苷酶和神经氨酸酶活性恢复到低对照水平。在加入校正因子后，免疫沉淀模式完全正常，并且成熟的64，000-道尔顿β-半乳糖苷酶在突变体成纤维细胞中积累。组合的β-半乳糖苷酶/神经氨酸酶缺乏可能是由缺陷的32，000-道尔顿糖蛋白引起的，该糖蛋白通常是保护β-半乳糖苷酶/神经氨酸酶所必需的。半乳糖苷酶和神经氨酸酶的活性，以防止过度的溶酶体内降解，并使这些酶具有充分的水解活性。
In normal human fibroblasts, an enzymically active 85,000-dalton precursor form of .beta.-galactosidase is processed, via a number of intermediates, into a mature 64,000-dalton form. In addition there is an enzymically inactive 32,000-dalton component and its 54,000-dalton precursor. In fibroblasts from patients with a combined deficiency of .beta.-galactosidase and neuraminidase these last 2 components are absent and hardly any mature .beta.-galactosidase can be demonstrated. Nevertheless, in the mutant fibroblasts, precursor .beta.-galactosidase is synthesized and processed normally. The excessive intralysosomal degradation that is responsible for the deficiency of mature .beta.-galactosidase can be partially corrected by addition of the protease inhibitor leupeptin, which results in the accumulation of 85,000-dalton precursor .beta.-galactosidase and of a partially processed 66,00-dalton form. When mutant cells were grown in the presence of a corrective factor purified from the medium of NH4Cl-stimulated cell cultures, both .beta.-galactosidase and neuraminidase activities were restored to low control levels. The immunoprecipitation pattern was completely normal after addition of the corrective factor, and mature 64,000-dalton .beta.-galactosidase accumulated in the mutant fibroblasts. The combined .beta.-galactosidase/neuraminidase deficiency is probably caused by a defective 32,000-dalton glycoprotein which is normally required to protect .beta.-galactosidase and neuraminidase against excessive intralysosomal degradation and to give these enzymes their full hydrolytic activity.