Question

The following peptide fragments were generated after digestion of an 11 amino acid
polypeptide with trypsin and separately with thermolysin:
Trypsin: PA, YI, YKA, FDRH
Thermolysin: HYI, PAYK, AFDR
What is the sequence of the parent polypeptide?

Please show how you arrived at your answer!

(Note that trypsin recognizes the basic amino acids lysine (K) and arginine (R) and cleaves the peptide bond just after those; thermolysin recognizes the aromatic amino acids tyrosine (Y), phenylalanine (F), tryptophan (W), along with leucine (L), isoleucine (I), valine (V) and at high pH, histidine (H) and cleaves the peptide bond just in front of one of these.)

Answer 1

total number of amino acids in a sequence = 11

after trypsin digestion we get PA YI YKA FDRH and after thermolysin digestion we get HYI PAYK AFDR

from digested products we got to know that after PA there is YK (thermolysin) but in trypsin digested product there is a product YKA that means there are 2 A so we get the sequence PAYKA .

after that from thermolysin product we get that after A there is FDR and after FDR H is present (trypsin digested product) and finally from thermolysin digested product we get HYI which indicates that after H there is YI that means there are two Y

so the 11 amino acid sequence is PAYKAFDRHYI