Question

When fumarate reacts with D₂O in the presence of the enzyme fumarase, only one isomer of the product is formed, as shown here. Is the enzyme catalyzing a syn or an anti-addition of D₂O?

Short answer

The enzyme catalyst is a syn-addition.

Step-by-step solution

Determination of the structure

The above enzyme catalysis reaction is an syn-addition. By converting the desired product in Fischer structure, we can understand whether the reaction will happen through Cis or anti addition.

Reaction mechanism

The reaction mechanism is given as follows,

From the given mechanism above, we can see the desired product resembles to Cis addition product. So, the mechanism is followed by Sin addition.