Chapter 5, Problem 51RE

Interpretation Introduction

Interpretation:

The chemical or enzyme used for cutting proteins into fragments, is to be identified.

Concept introduction:

Before the sequencing experiment of proteins takes place, the peptides are converted into small length peptides by the action of certain chemicals or enzymes that cut the proteins at specific points to yield smaller fragments of peptides. Examples of such chemicals or enzymes are trypsin, chymotrypsin, and cyanogen bromide.

The reagent cyanogen bromide cleaves the protein peptides at their internal residues of methionine.

The proteolytic enzyme trypsin cleaves the protein peptides at the sites where basic amino acid (histidine, lysine, and arginine) residues are present. But, as histidine is neutral in nature, trypsin does not react with it.

The proteolytic enzyme chymotrypsin cleaves the protein peptides at the sites where the aromatic amino acid (tryptophan, tyrosine, and phenylalanine) residues are present.