Cyanogen bromide, peptide bond hydrolysis

Cyanogen bromide (BrC=N) causes the hydrolysis of the amide bond on the C-side of a methionine residue. Cyanogen bromide is more specific than the endopeptidases about what peptide bonds it cleaves, so it provides more reliable information about the primary structure (the sequence of amino acids). Because cyanogen bromide is not a protein and therefore does not recognize the substrate by its shape, cyanogen bromide will still cleave the peptide bond if proline is at the cleavage site. 

Cyanogen bromide is specific for the cleavage of peptide bonds formed by the carboxyl group of methionine. Trypsin catalyzes the hydrolysis of peptide bonds formed by the carboxyl groups of arginine and lysine. 

Also suited for the specific enzymatic hydrolysis of peptide chains is the endoproteinase Glu-C from Staphylococcus aureus V8. It cleaves Glu-X bonds (ammonium carbonate buffer pH 7.8 or ammonium acetate buffer pH 4.0) as well as Glu-X plus Asp-X bonds (phosphate buffer pH 7.8). The most important chemical method for selective cleavage uses cyanogen bromide (BrCN) to attack Met-X-hnkages (Reaction 1.86). Hydrolysis of proteins with strong acids reveals a difference in the rates of hydrolysis of peptide bonds depending on the adjacent amino acid side chain. Bonds involving amino groups of serine and threonine are particularly susceptible to hydrolysis. This effect is due to... 

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