What is the oxyanion hole and why is it important?

Oxyanion holes are commonly found in many enzyme structures. They are crucial for the stabilization of high-energy oxyanion intermediates or transition states through hydrogen bonding.

What is the specificity of chymotrypsin?

Chymotrypsin, like most enzymes, is specific in the types of substrates with which it reacts. As a protease, it cleaves polypeptides, and its inherent specificity allows it to act only on the carboxy-terminal of aromatic residues.

How is oxyanion hole formed?

Abstract. The oxyanion hole of serine proteases is formed by the backbone N atoms of the catalytic Ser-195 and Gly-193 and engages the backbone O atom of the P1 residue of substrate in an important H-bonding interaction.

What is the specificity of trypsin?

Specificity: Trypsin cleaves peptides on the C-terminal side of lysine and arginine amino acid residues. If a proline residue is on the carboxyl side of the cleavage site, the cleavage will not occur. If an acidic residue is on either side of the cleavage site, the rate of hydrolysis has been shown to be slower.

What is a specificity pocket?

The substrate residue N-‐terminal to the cleavage site (P1) largely determines the specificity of serine proteases. P1 binds S1, which is called the specificity pocket; its interactions were found early on to be a major determinant of the substrate specificity for trypsin, chymotrypsin and elastase.

What stabilizes the oxyanion hole?

An oxyanion hole is a pocket in the active site of an enzyme that stabilizes transition state negative charge on a deprotonated oxygen or alkoxide. The pocket typically consists of backbone amides or positively charged residues.

What is specificity pocket?

What is more specific trypsin and chymotrypsin?

The main difference between trypsin and chymotrypsin lies in the specificity to the peptide bond cleavage with respect to the amino acid residue in the polypeptide chain. Chymotrypsin is specific for aromatic amino acids, whereas trypsin hydrolyses peptide bonds at the C-terminal side of lysine and arginine residues.

What is the oxyanion?

An oxyanion, or oxoanion, is an ion with the generic formula A. xO z− y (where A represents a chemical element and O represents an oxygen atom). Oxyanions are formed by a large majority of the chemical elements. The formulae of simple oxyanions are determined by the octet rule.

What is the purpose of the S1 specificity pocket in chymotrypsin?

The S1 pocket helps to explain why chymotrypsin, trypsin, and elastase cleave 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.

How is specificity determined by the serine proteases?