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Analysis of a hexapeptide using enzymatic cleavage reveals the following result:
• Amino acid composition of the peptide is: 2R, A,V, S, Y
• Trypsin digestion yields two fragments and the compositions are: (R, A, V) and (R, S, Y)
• Chymotrypsin digestion yields two fragments and the compositions are: (A, R, V, Y) and (R, S)
• Digestion with carboxypeptidase A yields no cleavage product.
Given:
Trypsin cleaves at carboxyl side of R.
Chymotrypsin cleaves at carboxyl side of Y.
Carboxypeptidase A cleaves at amino side of the C-terminal amino acid (except R and K) of the peptide.
The correct amino acid sequence of the peptide is:
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- RSYRVA
- AVRYSR
- SRYVAR
- SVRRYA
Correct Option: B
Trypsin cleaves at carboxy side of R. So R is written on the C termini. On the other hand, Trypsin digested fragment includes RAV And RSY. Any of the fragment can be placed depending on the chymotrypsin digestion which is performed after trypsinisation. Chymotripsinisation produced ARVY and SR after cleaving C termini of another R. So the resultant amino acid sequence will be AVRYSR.
