Freeze Hudson H
Glycobiology and Carbohydrate Chemistry Program, Burnham Institute for Medical Research, 10901 N. Torrey Pines Rd., La Jolla, CA, 92037, USA.
Curr Mol Med. 2007 Jun;7(4):389-96. doi: 10.2174/156652407780831548.
The Congenital Disorders of Glycosylation (CDG) are a collection of over 20 inherited diseases that impair protein N-glycosylation. The clinical appearance of CDG patients is quite diverse making it difficult for physicians to recognize them. A simple blood test of transferrin glycosylation status signals a glycosylation abnormality, but not the specific defect. An abnormal trasferrin glycosylation pattern suggests that the defect is in either genes that synthesize and add the precursor glycan (Glc(3)Man(9)GlcNAc(2)) to proteins (Type I) or genes that process the protein-bound N-glycans (Type II). Type I defects create unoccupied glycosylation sites, while Type II defects give fully occupied sites with abnormally processed glycans. These types are expected to be mutually exclusive, but a group of patients is now emerging who have variable coagulopathy and hypoglycemia together with a combination of Type I and Type II transferrin features. This surprising finding makes identifying their defects more challenging, but the defects and associated clinical manifestations of these patients suggest that the N-glycosylation pathway has some secrets left to share.
糖基化先天性疾病（CDG）是一组超过20种的遗传性疾病，会损害蛋白质的N-糖基化。CDG患者的临床表现非常多样，这使得医生很难识别他们。一项简单的转铁蛋白糖基化状态血液检测能显示糖基化异常，但无法确定具体缺陷。转铁蛋白糖基化模式异常表明缺陷存在于合成并将前体聚糖（Glc(3)Man(9)GlcNAc(2)）添加到蛋白质的基因（I型）或处理与蛋白质结合的N-聚糖的基因（II型）中。I型缺陷会产生未被占据的糖基化位点，而II型缺陷会产生被完全占据但聚糖加工异常的位点。预计这两种类型是相互排斥的，但现在出现了一组患者，他们既有可变的凝血病和低血糖，又同时具有I型和II型转铁蛋白特征。这一惊人发现使得识别他们的缺陷更具挑战性，但这些患者的缺陷及相关临床表现表明N-糖基化途径还有一些秘密有待揭示。
