Definition: A control interaction in which a physical entity (a catalyst) increases the rate of a conversion interaction by lowering its activation energy. Instances of this class describe a pairing between a catalyzing entity and a catalyzed conversion. Comment: A separate catalysis instance should be created for each different conversion that a physicalEntity may catalyze and for each different physicalEntity that may catalyze a conversion. For example, a bifunctional enzyme that catalyzes two different biochemical reactions would be linked to each of those biochemical reactions by two separate instances of the catalysis class. Also, catalysis reactions from multiple different organisms could be linked to the same generic biochemical reaction (a biochemical reaction is generic if it only includes small molecules). Generally, the enzyme catalyzing a conversion is known and the use of this class is obvious. In the cases where a catalyzed reaction is known to occur but the enzyme is not known, a catalysis instance should be created without a controller specified (i.e. the CONTROLLER property should remain empty). Synonyms: facilitation, acceleration. Examples: The catalysis of a biochemical reaction by an enzyme, the enabling of a transport interaction by a membrane pore complex, and the facilitation of a complex assembly by a scaffold protein. Hexokinase -> (The "Glucose + ATP -> Glucose-6-phosphate +ADP" reaction). A plasma membrane Na+/K+ ATPase is an active transporter (antiport pump) using the energy of ATP to pump Na+ out of the cell and K+ in. Na+ from cytoplasm to extracellular space would be described in a transport instance. K+ from extracellular space to cytoplasm would be described in a transport instance. The ATPase pump would be stored in a catalysis instance controlling each of the above transport instances. A biochemical reaction that does not occur by itself under physiological conditions, but has been observed to occur in the presence of cell extract, likely via one or more unknown enzymes present in the extract, would be stored in the CONTROLLED property, with the CONTROLLER property empty.
Source:http://www.biopax.org/release/biopax-level2.owl#catalysis