This class describes most forms of protein, RNA or activity regulation. Regulation can be either by a direct influence on the protein’s activity (e.g. allosteric inhibition of an enzyme) or by influencing the quantity of active protein available (e.g. by inducing or blocking its transcription or translation). The one form of regulation that is not covered by this class is when the quantity of a protein is regulated as a result of chemical or binding reactions that either produce or consume the active form of a protein – these are represented as Reactions instead. There can be some ambiguity as to what should be represented as a reaction and what should be represented as a regulation event. In general, an event that can be represented as a reaction should be when a) there is sufficiently detailed information known to model it as a reaction, b) both reactants and products exist as stable, independent entities, and c) our schema supports referring to both reactant and product of the reaction independently and there is some justification for wanting to go down to that level of detail. For example, a transcription factor bound to a small molecule will generally have a different activity than the unbound transcription factor. This could be represented either as the reaction TF + x -¿ TF-x or as a regulation event in which x activates or inhibits the activity of TF. However, because both TF and TF-x are stable molecules which can potentially regulate different transcription units (not all will, but some do), or TF could bind another small molecule y and regulate yet another set of transcription units, we prefer to model this kind of interaction as a reaction when the data is available. On the other hand, an enzyme binding to some inhibitor could also be represented as a reaction, but since there is rarely any reason to refer to the enzyme-inhibitor complex outside of the context of the reaction the enzyme catalyzes, we choose instead to model these events as regulation events in which the inhibitor regulates the activity of the enzyme. Instances of this class represent a one-to-one mapping between regulator and regulatedentity (i.e. an entity may regulate many processes, or a process may be regulated by many entities, but each one requires its own instance of Regulation to represent it)