Question 16.CC.4: Structure and Names of Peptides Consider the dipeptide Val–P......
Structure and Names of Peptides
Consider the dipeptide Val–Pro:
a. What amino acid is the N terminal amino acid?
b. What amino acid is the C terminal amino acid?
c. How are the amino acids connected?
d. Give the name of the dipeptide.
e. Give the name of the dipeptide in which the amino acid order is reversed as Pro–Val.
a. Valine, the first amino acid in the peptide, has a free — {\mathrm{NH}_{3}}^+ , which makes it the N terminal amino acid.
b. Proline, the last amino acid in the peptide, has a free —COO¯ which makes it the C terminal amino acid.
c. The amino acids valine and proline are connected by a peptide bond, which is an amide bond between the C=O of valine and the N—H of proline.
d. In the dipeptide Val–Pro, the N terminal amino acid, valine, is named valyl and the C terminal amino acid, proline, retains its name. The dipeptide is named valylproline.
e. In the dipeptide Pro–Val, the N terminal amino acid, proline, is named prolyl and the C terminal amino acid, valine, retains its name. The dipeptide is named prolylvaline.