Question

Question #1 (Total: 40 %) N-Acetylglucosamine is commonly known as an amide derivative of the monosaccharide glucose with the following structure: Он Но- Но- OH NH CHз You are told that the B1 group of N-Acetylglucosamine is chemically linked to a side-chain of the following peptide (through a "glucosidic-like" bond): Phe-Gly-Ser-Ala Please propose a mechanism in the coupling between N-Acetylglucosamine and Phe-Gly- Ser-Ala. [15 points] Please clearly show the linkage between N-Acetylglucosamine and Phe-Gly-Ser-Ala in a detailed diagram. [25 points]

Answer 1

In the given peptide, Phe-Gly-Ser-Ala; Phenylalanine (Phe) is the N-terminal amino acid, whereas Alanine (Ala) is the C-terminal amino acid.

Now, the OH-group attached to the methylene group of N-Acetylglucosamine is linked to the C-terminal amino acid (Ala) of the given peptide.

The mechanism and the linkage between N-Acetylglucosamine and the given peptide can be written as follows.

Date CH N. oH,N N (40 ČHOH N H Phe-gly-ser-pla Сңрв -OM но NH

Note: This proceeds according to the esterification reaction (carboxylic acid + alcohol ----> ester)