Chapter 19, Problem 19.95QP

Interpretation Introduction

Interpretation:

The complete structural formula for the peptide tyr-lys-ala-phe has to be drawn and the bond that is broken under action of chymotrypsin has to be determined.

Concept Introduction:

Proteolytic enzymes that cleave the peptide bond are found in the pancreases and are often referred to as serine proteases because of the presence of a nucleophilic serine at the active site of the active site. They are classified on the basis of the substrate specificity. For example, the trypsin cleaves specifically at the carboxyl end of positively charged amino acids such as arginine or lysine except for the cases when they are followed by amino acid proline.

Chymotrypsin cleaves at the carboxyl-terminal of aromatic amino acids such as phenylalanine, tyrosine, and tryptophan. Elastase cleaves at the carboxyl-terminal of valine serine alanine, leucine, glycine, or isoleucine.