91Ó°ÊÓ

The method of sequencing peptides without disturbing the peptide bonds is Edman degradation. During this method, N-terminal amino acid Leu is cleaved first.

The sequence becomes like this in the given heptapeptide:

³¢±ð³Ü–_³å³å–_³å³å–_³å³å–_³å³å–_³å³å–_³å³å

The treatment of heptapeptide with chymotrypsin forms a hexapeptide and a single amino acid since chymotrypsin cleaves at an amide bond with a carbonyl group from Phe, Tyr, or Trp.

The sequence becomes like this in the given heptapeptide:

³¢±ð³Ü–_³å³å–_³å³å–_³å³å–_³å³å–_³å³å–G±ô³Ü

Partial hydrolysis forms Glu, Leu, Phe, and the tripeptidesGly–Ala–Ser and Ala–Ser–Arg

Hence, the sequence becomes:

³¢±ð³Ü–G±ô²â–A±ô²¹â€“S±ð°ù–A°ù²µâ€“_³å³å–G±ô³Ü

or

³¢±ð³Ü–_³å³å–G±ô²â–A±ô²¹â€“S±ð°ù–A°ù²µâ€“G±ô³Ü

Cleavage by trypsin is after Arg and yields a dipeptide; therefore, this must be the peptide:

³¢±ð³Ü–G±ô²â–A±ô²¹â€“S±ð°ù–A°ù²µâ€Ñï³ó±ð–G±ô³Ü