Light and heavy lysosomes: characterization of N-acetyl-beta-D-hexosaminidase isolated from normal and I-cell disease lymphoblasts.
Light and heavy lysosomes: characterization of N-acetyl-beta-D-hexosaminidase isolated from normal and I-cell disease lymphoblasts.
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轻溶酶体和重溶酶体：从正常和 I 细胞疾病淋巴母细胞中分离的 N-乙酰基-β-D-氨基己糖苷酶的表征。
DOI：
10.1093/glycob/3.4.313
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发表时间：
1993
期刊：
影响因子：
4.3
通讯作者：
Wright,D
中科院分区：
文献类型：
--
作者：
Miller,AL;Norton,V;Robertson,R;Jenks,M;Yeh,RY;Wright,D
我们以前报道过，即使n -乙酰氨基-1-磷酸转移酶活性严重抑制或缺失，i细胞病淋巴母细胞仍能维持正常或接近正常的细胞内溶酶体酶水平（Littleet al., Biochem）。J., 248, 151-159, 1987)。本研究采用胶体硅梯度亚细胞分离，表明从i细胞病和伪hurler多营养不良淋巴细胞中分离的轻溶酶体和重溶酶体具有正常的n -乙酰-β- d -己糖氨酸酶、α- d -甘露糖苷酶和β- d -葡萄糖醛酸酶的特异性活性水平。这些目前的发现与来自同一患者的培养成纤维细胞形成对比，其中发现溶酶体内酶活性降低。蓖麻的柱层析显示，与来自相应正常对照的酶相比，来自淋巴母细胞的重i细胞病溶酶体和轻i细胞病溶酶体中的n -乙酰基-β- d -己糖氨酸酶具有更多可接近的半乳糖残基（30-50%）。对来自i细胞溶酶体的n -乙酰-β- d -己糖氨基酶的Endo-β- n -乙酰葡萄糖氨基酶H处理表明，大多数新合成的高甘露糖型低聚糖链在被转运到溶酶体之前被修饰成复合型碳水化合物。淋巴母细胞的这一结果不同于先前在成纤维细胞中的发现，在成纤维细胞中，来自i细胞疾病和伪hurler多营养不良溶酶体的乙酰-β- d -己糖氨酸酶表现出主要与高甘露糖型低聚糖链相关的特性。目前的结果表明，不同的细胞类型可能以不同的方式修饰溶酶体酶的碳水化合物侧链，并且所选择的细胞类型也可能采用甘露糖-6-磷酸途径以外的机制将溶酶体酶靶向溶酶体。
We previously reported that I-cell disease lymphoblasts maintain normal or near-normal intracellular levels of lysosomal enzymes, even thoughN-acetylglucosamine-1-phosphotransferase activity is severely depressed or absent (Littleet al., Biochem. J., 248, 151–159, 1987). The present study, employing subcellular fractionation on colloidal silica gradients, indicates that both light and heavy lysosomes isolated from I-cell disease and pseudo-Hurler polydystrophy lymphoblasts possess normal specific activity levels ofN-acetyl-β-D-hexosaminidase, α-D-mannosidase and β-D-glucuronidase. These current findings are in contrast to those of cultured fibroblasts from the same patients, where decreased intralysosomal enzyme activities are found. Column chromatography onRicinus communisrevealed that N-acetyl-β-D-hexosaminidase in both heavy and light I-cell disease lysosomal fractions from lymphoblasts possesses an increased number of accessible galactose residues (30–50%) as compared to the enzyme from the corresponding normal controls. Endo-β-N-acetylglucos-aminidase H treatment ofN-acetyl-β-D-hexosaminidase from the I-cell lysosomal fractions suggests that the majority of newly synthesized high-mannose-type oligosaccharide chains are modified to complex-type carbohydrates prior to being transported to lysosomes. This result from lymphoblasts differs from previous findings with fibroblasts, whereN-acetyl-β-D-hexosaminidase from I-cell disease and pseudo-Hurler polydystrophy lysosomes exhibited properties associated with predominantly high-mannose-type oligosaccharide chains. The current results imply that different cell types may modify the carbohydrate side chains of lysosomal enzymes in a differential manner, and that selected cell types may also employ mechanisms other than the mannose-6-phosphate pathway for targeting lysosomal enzymes to lysosomes.