To allow UniProt to curate reactions at the level of specific enzymes instead of enzyme classes, and to use standardized names for reactants, we will use chemical reaction descriptions from the Rhea database whenever possible. For catalytic activities that can only be described in the form of free text, we will continue to follow the NC-IUBMB descriptions. In the future, we will also curate the physiological direction of a reaction, i.e. the direction of the net flow of reactants in vivo, where evidence for it is available.

For more details and examples, please have a look at this announcement: https://www.uniprot.org/help/catalytic_activity_change

This change is planned for December 5, 2018 at the earliest.