Abstract：
Alterations to N-glycan expression are relevant to the progression of various diseases, particularly cancer. In many cases, specific N-glycan structural features such as sialylation, fucosylation, and branching are of specific interest. A novel MALDI imaging mass spectrometry workflow has been recently developed to analyze these features of N-glycosylation through the utilization of endoglycosidase enzymes to cleave N-glycans from associated glycoproteins. Enzymes that have previously been utilized to cleave N-glycans include peptide-N-glycosidase F (PNGase F) to target N-glycans indiscriminately and endoglycosidase F3 (Endo F3) to target core fucosylated N-glycans. In addition to these endoglycosidases, additional N-glycan cleaving enzymes could be used to target specific structural features. Sialidases, also termed neuraminidases, are a family of enzymes that remove terminal sialic acids from glycoconjugates. This work aims to utilize sialidase, in conjunction with PNGase F/Endo F3, to enzymatically remove sialic acids from N-glycans in an effort to increase sensitivity for nonsialylated N-glycan MALDI-IMS peaks. Improving detection of nonsialylated N-glycans allows for a more thorough analysis of specific structural features such as fucosylation or branching, particularly of low abundant structures. Sialidase utilization in MALDI-IMS dramatically increases sensitivity and increases on-tissue endoglycosidase efficiency, making it a very useful companion technique to specifically detect nonsialylated N-glycans.
摘要：
N-聚糖表达的改变与各种疾病的进展有关。尤其是癌症。在许多情况下,特定的N-聚糖结构特征，如唾液酸化，岩藻糖基化,和分支是特别感兴趣的。最近开发了一种新的MALDI成像质谱工作流程，通过利用内切糖苷酶从相关糖蛋白切割N-聚糖来分析N-糖基化的这些特征。先前已用于切割N-聚糖的酶包括肽-N-糖苷酶F(PNGaseF)以不加选择地靶向N-聚糖和内切糖苷酶F3(EndoF3)以靶向核心岩藻糖基化N-聚糖。除了这些内切糖苷酶，另外的N-聚糖裂解酶可用于靶向特定的结构特征。唾液酸酶,也称为神经氨酸酶，是从糖缀合物中去除末端唾液酸的酶家族。这项工作的目的是利用唾液酸酶，与PNGaseF/EndoF3结合，从N-聚糖中酶法去除唾液酸，以提高对非唾液酸化N-聚糖MALDI-IMS峰的敏感性。改善非唾液酸化N-聚糖的检测可以更彻底地分析特定的结构特征，如岩藻糖基化或分支，特别是低丰度结构。MALDI-IMS中的唾液酸酶利用率显着提高了灵敏度并提高了组织内切糖苷酶的效率，使其成为专门检测非唾液酸化N-聚糖的非常有用的辅助技术。
