MBB 222 Study Guide - Midterm Guide: Scissile Bond, Aromatic Amino Acids, Catalytic Triad

• School: Simon Fraser University
• Department: Molec Biol & Biochem
• Course: MBB 222
• Professor: Adam Barlev

Document Summary

One of the important features of serine proteases is that the size of the enzyme active site of three closely related proteins chymotrypsin, trypsin, and elastase imparts a degree of substrate specificity. Chymotrypsin, for example, contains a hydrophobic region in the substrate binding pocket that can accommodate proteins with aromatic amino acids adjacent to the scissile peptide bond. In contrast, a region of the substrate binding pocket of trypsin is much deeper and contains a negatively charged asp residue at the bottom (figure 7. 29). This substrate specificity pocket explains why trypsin cleaves proteins at peptide bonds bordering positively charged lysine and arginine residues. This structure is consistent with the observation that the natural substrate of elastase, the fibrous protein elastin, is rich in glycine and alanine residues. The carboxyl-terminal fragment is released as the first product. First tetrahedral intermediate formed (c , o from carbonyl group but now single bonded,