Extracellular superoxide dismutase (EC-SOD, SOD3) protects tissues against oxidative damage by detoxifying superoxide anions, particularly in the lungs and cardiovascular system. EC-SOD undergoes several posttranslational modifications including N-glycosylation and proteolytic cleavage. While the roles of proteolytic cleavage have been well studied, the structure and function of EC-SOD N-glycans are poorly understood. Here we analyzed glycan structures on native EC-SOD purified from human sera, and identified sialylated biantennary structures. Using glycan maturation-defective CHO mutant cells, we further revealed that the presence of terminal sialic acids in the N-glycans of EC-SOD enhanced both the secretion and furin-mediated C-terminal cleavage of EC-SOD. These results provide new insights into how the posttranslational modifications of EC-SOD control its functions.

中文翻译：

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胞外超氧化物歧化酶（EC-SOD）的唾液酸化增强弗林蛋白酶介导的裂解和分泌

细胞外超氧化物歧化酶（EC-SOD，SOD3）通过使超氧化物阴离子解毒来保护组织免受氧化损伤，尤其是在肺部和心血管系统中。EC-SOD经历了几种翻译后修饰，包括N-糖基化和蛋白水解切割。尽管已经很好地研究了蛋白水解裂解的作用，但是对EC-SOD N-聚糖的结构和功能的了解却很少。在这里，我们分析了从人血清中纯化得到的天然EC-SOD上的聚糖结构，并确定了唾液酸化的双触角结构。使用聚糖成熟缺陷的CHO突变细胞，我们进一步揭示了N中末端唾液酸的存在EC-SOD的β-聚糖增强了EC-SOD的分泌和弗林蛋白酶介导的C末端裂解。这些结果为EC-SOD的翻译后修饰如何控制其功能提供了新的见解。