Structural Biochemistry/Enzyme Catalytic Mechanism/Enzyme Classification/Isomerases

Isomerases are a class of enzymes that catalyze the conversion of one isomer into another. Isomerases catalyze reactions of the form A to B. Triose phosphate isomerase (TPI) is a prime example of an isomerase. TPI catalyzes the isomerization of a ketose into an aldose by catalying the transfer of a hydrogen atom from carbon-1 to carbon-2. Isomerases can also be used to catalyze the isomerization of aldoses to ketoses.

TPI uses glutamate as a base to abstract a proton from the carbon-1. Histidine is used as an acid to donate a proton to the oxygen bonded to carbon-2, this intermediate is known as the enediol intermediate. The glutamic acid then donates a proton to carbon-2 while histidine removes a proton from the hydroxyl group on carbon-2, forming an aldose.

Examples of Isomerases

A page with a list of Isomerases can be found here [[1]]