The enzyme binds the closed form of the sugar and catalyzes ring opening to generate a form of open-chain conformation that facilitates the isomerization reaction, which proceeds via an ene- diol mechanism.
The enzyme from Escherichia coli can also convert D-arabinose to D-ribulose.
The enzyme from the thermophilic bacterium Caldicellulosiruptor saccharolyticus also converts D-altrose to D-psicose and L-galactose to L-tagatose.