catalysisDirection

This property represents the direction of this catalysis under all physiological conditions if there is one. Note that chemically a catalyst will increase the rate of the reaction in both directions. In biology, however, there are cases where the enzyme is expressed only when the controlled bidirectional conversion is on one side of the chemical equilibrium [todo : example]. If that is the case and the controller, under biological conditions, is always catalyzing the conversion in one direction then this fact can be captured using this property. If the enzyme is active for both directions, or the conversion is not bidirectional, this property should be left empty.

Source:http://www.biopax.org/release/biopax-level3.owl#catalysisDirection