Question

Name: 09) (5 points) Trypsin and chymotrypsin are members of the family of serine proteases - they cleave (cut) peptide bonds at the C-terminal end of specific residues. a) Chymotrypsin cleaves peptide bonds at the C-terminal end of what type of amino acid? b) Briefly describe the specific properties of the binding pocket in chymotrypsin that allows proper orientation of the substrate to cleave at the position you described in (a). c) Trypsin cleaves peptide bonds at the C-terminal end of arginine and lysine residues. Given what you know about Arg and Lys side chains, predict the size/shape and specific interactions that would provide trypsin's substrate-binding specificity.

Answer 1

Answers -

(a) The Enzyme Chymotrypsin Cuts the Aromatic Ring containing Amino acids like - Tryptophan (W), Tyrosin (Y), and Phenylalanine (F) .

*****For Just a joke you can keep in your mind that Chymotrypsin defeats WYF (wife).**********

(b) The S1 pockets of the chymotrypsin, . The S1 pocket helps to explain why chymotrypsin, cleaves certain peptide binds. The S1 pocket is a deep hydrophobic pocket that allows long, uncharged amino acids like phenylalanine and tryptophan to fit in chymotrypsin. Amino acids like - Tryptophan (W), Tyrosin (Y), and Phenylalanine (F) . These amino acids contain an aromatic ring in their side chain that fits into a hydrophobic pocket (the S1 position) of the enzyme. It is activated in the presence of trypsin.

(c) Mechanism of trypsin cleavage- The negative aspartate residue (Asp 189) located in the catalytic pocket (S1) of trypsin is responsible for attracting and stabilizing positively charged lysine and/or arginine, and is, thus, responsible for the specificity of the enzyme.

This means that trypsin predominantly cleaves proteins at the carboxyl side (or "C-terminal side") of the amino acids lysine and arginine except when either is bound to a C-terminal proline, although large-scale mass spectrometry data suggest cleavage occurs even with proline. Trypsin is considered an endopeptidase, i.e., the cleavage occurs within the polypeptide chain rather than at the terminal amino acids located at the ends of polypeptides.

******In case of any query , you may please comment, I would sure try to help.******

Thanks