What is the role of Ser 195 in chymotrypsin?

In the chymotrypsin/trypsin family, the oxyanion binding site is formed by the backbone amide nitrogens of Gly193 and Ser195. The nucleophilic attack by the Oγ of Ser195 on the carbonyl carbon atom of the substrate changes the geometry around this carbon from trigonal planar to tetrahedral.

What does ASP 102 do in chymotrypsin?

Asp-102 remains negatively charged throughout the catalytic cycle. It forms a salt bond with the protonated but not the deprotonated form of His-57, thereby stabilizing the protonated form and increasing the proton affinity of the histidine.

What does ASP do in catalytic triad?

These three amino acids are often referred to as a catalytic triad. As the serine oxygen attacks the carbonyl carbon of a peptide bond, the hydrogen-bonded His functions as a general base to abstract the serine proton, and the negatively charged Asp stabilizes the positive charge that forms on the His residue.

What does his 57 do?

The serine–protease mechanism requires that His-57 act as a base in activating each of the nucleophilic-attack steps, as an acid in transferring a proton to each leaving group.

What is the role of histidine 57 in the function of chymotrypsin?

In the second step water is the nucleophile that attacks the acyl-enzyme intermediate. Explain the function of histidine 57 in the mechanisn of chymotrypsin. Histidine performs a series of steps involving general base catalysis followed by general acid catalysis.

What does His 57 do?

What does serine protease do?

Serine proteases (or serine endopeptidases) are enzymes that cleave peptide bonds in proteins. Serine serves as the nucleophilic amino acid at the (enzyme’s) active site. They are found ubiquitously in both eukaryotes and prokaryotes.

How does serine protease work?

Serine proteases catalyze peptide bond hydrolysis in two sequential steps. In the first (acylation) reaction, the nucleophilic serine attacks the substrate scissile bond, forming first a tetrahedral intermediate and then a covalent acyl-enzyme with release of the C-terminal fragment.

What amino acids does chymotrypsin cleave?

Chymotrypsin (EC 3.4. 21.1) is a 26kDa serine carboxypeptidase that preferentially cleaves the amide bond (the P1 position) of an aromatic amino acid residues such as tyrosine, tryptophan and phenylalanine.