BIOC 3560 Lecture Notes - Lecture 8: Serine Protease, Aromatic Amino Acids, Chymotrypsin
25 Oct 2018
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Document Summary
Some enzymes are synthesized as an inactive precursor. These enzymes are termed a zymogen if activated by a protease or a proenzyme if activated by a non-protease. Zymogens are activated by the cleavage of specific peptide bonds (s) This allows conformational changes in the enzyme to expose the active site. During digestion, dietary proteins must be broken down into small peptides by proteases. Chymotrypsin is one of several proteases that cuts peptides at specific locations on the peptide backbone. This protease is able to cleave the peptide bond adjacent to aromatic amino acids. Many digestive system proteases are activated by proteolysis. His57 must be deprotonated: this allows his57 to act as a proton acceptor, including nucleophilic character in. Ser195 (critical to reaction mechanism: ser195 acts as a nucleophile and attacks carbonyl group on substrate. -amino group (newly formed as a result of proteolytic cleavage by trypsin) of ile16 must be protonated.
