This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
[{'content': 'If chymotrypsin molecule undergoes a ser-195-ala mutation then - \nSelect and explain. \nA. Chymotrypsin will not bind the substrate, B. Chymotrypsin will bind the substrate as well as cause cleavage, C. Chymotrypsin will bind the substrate but will not cause cleavage, D. No affect will be observed', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The substrate binds but does not cleave\xa0\n\nSerine-195 is involved in catalytic activity but not in binding.\nSerine-195 is the highly reactive residue of chymotrypsin.\nThe peptide bond is hydrolyzed through the acid-catalyzed nucleophilic attack, utilizing the serine 195 residue of the enzyme.\nThe enzyme-substrate complex is formed by the binding of the aromatic amino acid residue with the hydrophilic pocket on the active site of the enzyme (ser-195 has no role in binding).\nBinding of substrate initiates proton shifts that in effect transfer the hydroxyl proton of ser 195 to Asp 102. This results in the formation of a covalent acyl-enzyme intermediate.\nFurther proton on Asp 102 then shuttles through His 57 to the amino group and the peptide bond is cleaved.\nThus, Asp 102-His 57-ser 195 constitute a "charge-relay network" that functions as a "proton shuttle".', 'role': 'assistant'}]