Biochemistry 6th Edition by Reginald Garrett,Charles Grisham

Exercise 2

Solving the sequence of an oligopeptide from sequence analysis data
Amino acid analysis of an oligopeptide 7 residues long gave
Asp Leu Lys Met Phe Tyr
The following facts were observed:
a. Trypsin treatment had no apparent effect.
b. The phenylthiohydantoin released by Edman degradation was

c. Brief chymotrypsin treatment yielded several products including a dipeptide and a tetrapeptide. The amino acid composition of the tetrapeptide was Leu, Lys, and Met.
d. Cyanogen bromide treatment yielded a dipeptide, a tetrapeptide, and free Lys. What is the amino acid sequence of this heptapeptide?