中文摘要
N-glycosylation在真核細胞的幾個生理過程中起重要作用。在許多情況下，N-Glycan可以通過防止蛋白水解來延長蛋白質的穩定性和半衰期，因此，了解聚醣對蛋白質結構的作用是非常重要的。在蛇毒的結構中也含有 N-glycan，然而他的功能仍然不清楚。
在這項研究中，我們鑑定了來自Naja atra的Atragin和K-like兩種SVMP對其反應物纖維蛋白原（Fg）和N-Glycan作用的酶活性。結果顯示K-like和Atragin在選擇Fg上的差異切割位點的明顯證據。對於K-like，當與其他SVMP比較時，它在Lys413↓Leu414位置具有相同的切割位點。相比之下，Atragin切割了兩個不同的α-chain位置，並在用Fg處理Atragin後立即發生反應。有趣的是，添加N-聚醣可以影響兩種SVMP的酶活性：末端的唾液酸不僅保證穩定，而且還抑制K-like酶活性。而肝素促進Fgβ-chain 的Atragin酶活性。基於該結果，我們提出了針對Fg的K-like和Atragin的示意模型，以解釋末端N-glycan和heparin影響SVMP酶活性的作用。

ABSTRACT
N-linked glycosylation plays an essential role in several physiological processes of eukaryotic cell. N-glycan can prolong the stability and half-life time of protein in many cases by protection against proteolysis, therefore, the understanding about the role of glycan on protein structure is very important. In the structure of snake venom also contain N-glycosylation, however, the function of it still remaining unclearly understood.
In this study, we identified the enzymatic activity of two SVMPs from Naja atra, Atragin and K-like, on its substrate Fibrinogen (Fg) and the role of N-glycan. The results shown clearly evidence that K-like and Atragin chosen the differential cleavage site on Fg. For K-like, it has the same cleavage site at position Lys413↓Leu414 when compare with others SVMP. In contrast, Atragin cleaved two different position of α-chain, that’s reaction occurred immediately after treat Atragin with Fg. Interestingly, the addition of N-glycan can mediate enzymatic activity of the two SVMP: The Terminal Sialic Acid not only warrant the stable but also prevent enzymatic of K-like, whereas Heparin promoted Atragin enzymatic activity on β-chain of Fg. Based on the results, we propose the schematic model for K-like and Atragin against Fg to explain the role of Terminal Sialic Acid and Heparin to mediate enzymatic activity of SVMP.

LIST OF CONTENT
I. INTRODUCTION 1
1.1 Venoms and toxins 1
1.2 Venom protease 2
1.2.1 ADAMs family 4
1.2.2 Snake venom metalloproteinase (SVMP) 5
1.2.2.1 P-I snake venom metalloproteinase 6
1.2.2.2 P-II snake venom metalloproteinase 6
1.2.2.3 P-III snake venom metalloproteinase 7
1.3 Effects of Glycosylation on Protease 8
1.3.1 N-glycosylated of ADAM and SVMPs 9
1.3.2 Glycosylation effect on protein stability 9
1.4 Heparin 10
1.5 Fibrinogen 10
II. MATERIALS AND METHODS 20
2.1 Materials 20
2.2 Methods 20
2.2.1 Purification of Atragin and Kaouthiagin-like 20
2.2.2 Measurement SVMP’s proteolytic activity 21
2.2.3 Transfer from gel to membrane for N-terminals analysis (wet transfer). 22
2.2.4 Isothermal titration calorimetry measurements 22
2.2.5 Fluorescence Measurement 23
2.2.6 N-terminal sequence analysis 23
III. RESULTS 24
3.1 Terminal Sialic acid of N-glycan inhibit K-like SVMP activities 24
3.2 Heparin binding and enhancing Atragin SVMP functions 25
3.3 Identified the cleavage sites of fibrinogen by K-like and Atragin 25
3.4 Modification structure of SVMP with N-glycan. 25
IV. DISCUSSIONS 36
References 44
Appendix table 54

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