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首页> 外文期刊>The biochemical journal >Degradation of keratan sulphate by β-N-acetylhexosaminidases A and B
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Degradation of keratan sulphate by β-N-acetylhexosaminidases A and B

机译：通过β-n-乙酰己胺蛋白酶A和B降解角蛋白硫酸盐的降解

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pEnzymic cleavage of beta-N-acetylglucosamine residues of keratan sulphate was studied iin vitro/i by using substrate a [3H]glucosamine-labelled desulphated keratan sulphate with N-acetylglucosamine residues at the non-reducing end. Both lysosomal beta-N-acetylhexosaminidases A and B are proposed to participate in the degradation of keratan sulphate on the basis of the following observations. Homogenates of fibroblasts from patients with Sandhoff disease, but not those from patients with Tay–Sachs disease, were unable to release significant amounts of N-acetyl[3H]glucosamine. On isoelectric focusing of beta-N-acetylhexosaminidase from human liver the peaks of keratan sulphate-degrading activity coincided with the activity towards p-nitrophenyl beta-N-acetylglucosaminide. A monospecific antibody against the human enzyme reacted with both enzyme forms and precipitated the keratan sulphate-degrading activity. Both isoenzymes had the same apparent Km of 4mM, but the B form was approximately twice as active as the A form when compared with the activity towards a chromogenic substrate. Differences were noted in the pH–activity profiles of both isoenzymes. Thermal inactivation of isoenzyme B was less pronounced towards the polymeric substrate than towards the p-nitrophenyl derivative./p
机译：通过使用基质A [3H]氨基葡萄糖标记的脱硫角酸硫酸盐在体外研究了角蛋白硫酸盐的β-乙酰甘氨酸胺残基的酶乳酸β-乙酰甘氨酸胺残留物。在非还原端的N-乙酰葡糖胺残留物。溶酶体β-N-乙酰己酶A和B都被提出在基于以下观察结果的基础上参与角蛋白硫酸盐的降解。 Sandhoff疾病患者的成纤维细胞匀浆，但不是来自Tay-Sachs疾病的患者的成纤维细胞，不能释放大量的N-乙酰基[3H]葡糖胺。在人肝中β-N-乙酰己氨基氨基氨基氨基氨基氨基氨基磷酶的硫酸盐降解活性的峰值与朝向硝基苯基β-N-乙酰葡糖胺胺的活性相符。针对人酶的单特异性抗体与两种酶形式反应并沉淀出角蛋白硫酸盐降解活性。两种同工酶具有相同的4mm表观km，但与朝向发色基质的活性相比，B形式大约是作为形式的活性的两倍。在两种同工酶的pH活性谱中发现了差异。同工酶B的热失活朝向聚合物基底比朝向对硝基苯基衍生物较小。

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