1. Acid hydrolysis: Ala , Arg, Lys , Met, Phe, Ser )

2. Carboxypeptidase A digestion: Ala

3. Trypsin digestion: (Ala, Arg), (Lys, Phe, Ser), (Lys), (Ala, Met, Ser)

4. CNBr treatment: (Ala, Arg, Lys , Met, Phe, Ser), (Ala, Ser)

5. Thermolysin digestion: (Ala), (Ala, Arg, Ser), (Lys , Met, Phe, Ser)

• (A) Ala-Lys-Ser-Arg-Lys-Phe-Met-Ser-Ala
• (B) Ala-Arg-Ser-Phe-Lys-Lys-Met-Ser
• (C) Ser-Arg-Ala-Phe-Lys-Ser-Met-Lys-Ala
• (D) Ala-Arg-Ser-Phe-Lys-Lys-Met-Ser-Ala

Solution

• 1. Acid hydrolysis indicates the amino acid composition of the polypeptide.
  
• 2. Carboxypeptidase A digestion suggests that the Cterminal amino acid is Ala.
• 3. Trypsin digestion cleaves the peptide bond after Arg and Lys residues, except when followed by Pro. This gives us the order of amino acids.
• 4. CNBr treatment cleaves the peptide bond after Met residues, indicating the presence of two Met residues in the sequence.
• 5. Thermolysin digestion cleaves the peptide bond after hydrophobic amino acids like Ala, Phe, and Met, and after Arg. This further confirms the order of amino acids.

Therefore, the polypeptide sequence is:

Ala-Arg-Ser-Phe-Lys-Lys-Met-Ser-Ala