Chorismate mutase is an enzyme that catalyzes the synthesis of prephenic acid from chorismic acid. I — Organic Chemistry Chemistry Question
Enzyme Reaction
Chorismate mutase is an enzyme that catalyzes the synthesis of prephenic acid from chorismic acid. It is an important step in the biosynthesis of aromatic amino acids such as phenylalanine and tyrosine.
pyruvic acid
During the transformation of shikimic acid to chorismic acid, dehydration is occurring. Choose the hydroxyl group in shikimic acid that is lost through above dehydration among all possible reactions.
Model Answer
Hydroxyl group No. 3
Chorismate mutase rearranges chorismic acid into prephenic acid without changing the molecular formula. Chorismic acid becomes prephenic acid through the Claisen rearrangement, a concerted pericyclic process like the Cope rearrangement as shown below:
D
D
D
D
design.
(c) Transition state of the reaction contains two six-membered rings with one chair and one twist-boat conformation.
(d) 7 and 8 can be distinguished on the basis of the 1H-NMR of Ha.
Model Answer
Correct statements: (a), (c), (d).
Draw the transition state of the transformation of chorismic acid to prephenic acid based on the TSA structures and their IC50 values.
Model Answer
Transition State
Compared with the uncatalyzed thermal conversion, chorismate mutase accelerates conversion of chorismic acid to prephenic acid 1.0×106 fold at 25 oC by lowering the activation energy of the reaction. Calculate the decrease in activation energy of chorismate mutase at 25 oC.
∆H≠ uncat is 86,900 J mol-1 for the thermal conversion of chorismic acid to prephenic acid. At what temperature will the rate of the uncatalyzed thermal conversion be the same as that of the enzyme-catalyzed conversion at 25 oC, assuming that Ea = ∆H≠.
Model Answer
For the enzyme-catalyzed reaction, Arrhenius equation could be applied.
k_cat / k_uncat = A exp (– Ea, cat / RT) / A exp (– Ea, uncat / RT) = exp [–∆Ea, cat-uncat / RT] = 1×10^6
–∆Ea, cat-uncat = 2,480 J mol-1 × ln 10^6
Therefore, –∆Ea, cat-uncat = 34,300 J mol-1