Abstract：
Glycosaminoglycans (GAGs) are sulfated polysaccharides comprising repeating disaccharides, uronic acid (or galactose) and hexosamines, including chondroitin sulfate, dermatan sulfate, heparan sulfate, and keratan sulfate. Hyaluronan is an exception in the GAG family because it is a non-sulfated polysaccharide. Lysosomal enzymes are crucial for the stepwise degradation of GAGs to provide a normal function of tissues and extracellular matrix (ECM). The deficiency of one or more lysosomal enzyme(s) results in the accumulation of undegraded GAGs, causing cell, tissue, and organ dysfunction. Accumulation of GAGs in various tissues and ECM results in secretion into the circulation and then excretion in urine. GAGs are biomarkers of certain metabolic disorders, such as mucopolysaccharidoses (MPS) and mucolipidoses. GAGs are also elevated in patients with various conditions such as respiratory and renal disorders, fatty acid metabolism disorders, viral infections, vomiting disorders, liver disorders, epilepsy, hypoglycemia, myopathy, developmental disorders, hyperCKemia, heart disease, acidosis, and encephalopathy. MPS are a group of inherited metabolic diseases caused by the deficiency of enzymes required to degrade GAGs in the lysosome. Eight types of MPS are categorized based on lack or defect in one of twelve specific lysosomal enzymes and are described as MPS I through MPS X (excluding MPS V and VIII). Clinical features vary with the type of MPS and clinical severity of the disease. This chapter addresses the historical overview, synthesis, degradation, distribution, biological role, and method for measurement of GAGs.
摘要：
糖胺聚糖（GAG）是包含重复二糖的硫酸化多糖，糖醛酸（或半乳糖）和己糖胺，包括硫酸软骨素,硫酸皮肤素,硫酸乙酰肝素，和硫酸角质素.透明质酸在GAG家族中是一个例外,因为它是非硫酸化多糖。溶酶体酶对于GAG的逐步降解至关重要，以提供组织和细胞外基质（ECM）的正常功能。一种或多种溶酶体酶的缺乏导致未降解GAG的积累，导致细胞，组织,和器官功能障碍。GAG在各种组织和ECM中的积累导致分泌到循环中,然后在尿液中排泄。GAG是某些代谢紊乱的生物标志物，如粘多糖（MPS）和粘多糖。GAG在患有各种疾病如呼吸和肾脏疾病的患者中也升高，脂肪酸代谢紊乱,病毒感染,呕吐障碍,肝脏疾病,癫痫,低血糖,肌病,发育障碍,高CK血症,心脏病,酸中毒,和脑病。MPS是一组遗传性代谢疾病，由溶酶体中降解GAG所需的酶缺乏引起。根据十二种特定溶酶体酶之一的缺乏或缺陷对八种类型的MPS进行分类，并将其描述为MPSI至MPSX（不包括MPSV和VIII）。临床特征随MPS的类型和疾病的临床严重程度而变化。本章介绍了历史概述，合成，降解，分布，生物学作用,和GAG的测量方法。
