In the chymotrypsin reaction mechanism there is a low-barrier hydrogen bond (LBHB) formed between: A) Asp¹⁰² and Ser¹⁹⁵. B) Asp¹⁰² and His⁵⁷. C) His⁵⁷ and Ser¹⁹⁵. D) Ser¹⁹⁵ and carbonyl oxygen in the peptide bond. E) None of the above.

Question

Quizplus · Accepted Answer

The low-barrier hydrogen bond (LBHB) in chymotrypsin mechanism is formed between Asp102 and His57. This interaction lowers the activation energy required for the nucleophilic attack of the serine residue in the active site on the peptide bond of the substrate. This activated serine forms the covalent intermediate which subsequently undergoes hydrolysis to release the products. Therefore, choice B, where Asp102 is interacting with His57, is the correct option. Choice A refers to Asp102 and Ser195, while choice C mentions His57 and Ser195, neither of which are correct. Choice D is also incorrect, as it refers to the carbonyl oxygen of the peptide bond and not the LBHB.

In the Chymotrypsin Reaction Mechanism There Is a Low-Barrier Hydrogen