33. The mechanism of chymotrypsin involves which of the following elements? (A) deprotonation of an active site Asp residue by His to start the reaction (B) formation of an acyl-enzyme intermediate that must be hydrolyzed to complete the reaction (C)stabilization of the positively charged His by a Gin residue (D) direct deprotonation of water by His to generate a hydroxide ion for initiation of the reaction (E) both a and b occur