Answer:
A. the rate of the acylation reaction being faster than the deacylation reaction.
Explanation:
Chymotrypsin belongs to a class of enzymes known as proteases; enzymes that catalyse the cleavage of peptide bonds by hydrolysis.
The mechanism of chymotrypsin catalysis occurs in two distinct phases; (1) an acylation phase where the peptide bond is cleaved and an ester linkage is formed between the peptide carbonyl carbon and the enzyme, (2) a deacylation phase where the ester linkage is hydrolyzed and the non-avylated enzyme is regenerated.
In studies by B.S. Hartley and B.A. Kilby in 1954 of chymotrypsin hydrolysis of the ester p-nitropheylacetate, as measured by the release of nitrophenol, it was discovered that it proceeded with a burst before leveling of to a slower rate. This burst was due to a rapid acylation of all the enzyme molecules with a slow deacylation limiting the turnover of the enzyme.
Similarly, the observation of burst kinetics in rapid kinetic studies of the hydrolysis of p-nitrophenylphosphate by chymotrypsin is due to the initial phase of acylation proceeding much faster than the later phase of deacylation of the enzyme.
