ECH is essential to metabolizing fatty acids in beta oxidation to produce both acetyl CoA and energy in the form of ATP.

In fact this enzyme is so efficient that the rate for short chain fatty acids is equivalent to that of diffusion-controlled reactions.

The two amino acids hold a water molecule in place, allowing it to attack in a syn addition to an α-β unsaturated acyl-CoA at the β-carbon.

What this implies is that the hydroxyl group and the proton from water are both added from the same side of the double bond, a syn addition.

This is made possible by the two glutamate residues which hold the water in position directly adjacent to the α-β unsaturated double bond.