28. PNGase F is the most effective enzyme for removing N-linked oligosaccharides from glycoproteins/glycopeptides. The glycan removal is accompanied by deamidation of the asparagine side-chain to which the N-linked oligosaccharides are attached. Which of the following statements is false about the target protein after PNGase F treatment?
(A) The molecular weight of the target protein will be reduced.
(B) The extinction coefficient at 280 nm of the target protein will be unchanged.
(C) The primary structure of the target protein will be the same.
(D) The target protein will gain additional aspartic acid residues.
(E) The isoelectric point of the target protein will be reduced.

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統計： A(0), B(0), C(1), D(1), E(2) #3167917

詳解 (共 1 筆)

#6293165
Answer: C
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來源：https://jcggdb.jp/GlycoPOD/protocolShow.action?nodeId=t58

A和D. PNGase F將醣基切下後產生aspartic acid，蛋白質總體的分子量會下降。
B. 280nm UV主要被tyrosine和tryptophan吸收，不會被醣基吸收，所以不影響。
C. 由於asparagine變成aspartic acid，所以primary structure會改變。
E. asparagine pI: 5.41
    asparatic acid: 2.77
(source: https://www.chem.ucalgary.ca/courses/351/Carey5th/Ch27/ch27-1-4-2.html)
所以asparagine變成aspartic acid會讓蛋白質整體的pI下降。
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