Examples of enzymes working in reverse?
Enzymes alter the rate of a reaction by lowering activation energy; they have no effect on the reaction equilibrium ($\ce{K_{eq}}$). Since $\ce{K_{eq}=\frac{k_f}{k_r}}$ and $\ce{K_{eq}}$ is constant, an increase in forward rate ($\ce{k_f}$) requires a corresponding increase in the reverse rate ($\ce{k_r}$). Intuitively it may help to think that the same effect an enzyme has on lowering the energy of the transition state in the forward direction should also be present in the reverse direction. Whether or not the reaction actually proceeds in reverse depends on the free energy difference between the reactants and products and their concentrations (among other things). See this answer for a great explanation.

Because their reactions are in equilibrium ($\Delta G\approx0,\ce{K_{eq}\approx1}$), many enzymes in the glycolytic pathway also catalyze the reverse reaction in gluconeogenesis. 



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