Question

Show the peptides that would result from cleavage by the indicated reagent:

a. Val-Arg-Gly-Met-Arg-Ala-Ser by carboxypeptidase A

b. Ser-Phe-Lys-Met-Pro-Ser-Ala-Asp by cyanogen bromide

c. Arg-Ser-Pro-Lys-Lys-Ser-Glu-Gly by trypsin

Short answer

1. Val-Arg-Gly-Met-Arg-AlaSer
2. Ser-Phe-Lys-Met Pro-Ser-Ala-Asp
3. ArgSer-Pro-Lys Lys Ser-Glu-Gly

Step-by-step solution

Specificity of carboxypeptidase A in protein cleavage

Carboxypeptidase A is specific to breaking the C-terminal amino acid. Therefore, the bond-breaking sites are:

Val-Arg-Gly-Met-Arg-Ala*-Ser

Specificity of cyanogen bromide in protein cleavage

Cyanogen bromide hydrolysis is on the C side of a Met. Therefore, the site of bond breaking is represented by *:

Ser-Phe-Lys-Met*-Pro-Ser-Ala-Asp

Specificity of trypsin in protein cleavage

Trypsin hydrolysis is the C-side of Arg and Lys. Therefore, the breaking of the bond takes place after Arg and Lys make three chain.

Arg*-Ser-Pro-Lys*-Lys-Ser-Glu-Gly