Reactome is an online bioinformatics database of biology described in molecular terms. The largest set of entries refers to human biology, but Reactome covers a number of other organisms as well. It is an on-line encyclopedia of core human pathways - DNA replication, transcription, translation, the cell cycle, metabolism, and signaling cascades - and can be browsed to retrieve up-to-date information about a topic of interest, e.g., the molecular details of the signaling cascade set off when the hormone insulin binds to its cell-surface receptor, or used as an analytical tool for the interpretation of large data sets like those generated by DNA microarray analysis. The information in Reactome is provided by expert biologists, called Curators, and gathered from the published research literature, is peer-reviewed before release on the Reactome website, and is periodically updated.
In Reactome, human biological processes are annotated by breaking them down into series of molecular events. Like classical chemistry reactions each Reactome event has input physical entities (substrates) which interact, possibly facilitated by enzymes or other molecular catalysts, to generate output physical entities (products).
Reactions include the classical chemical interconversions of intermediary metabolism, binding events, complex formation, transport events that direct molecules between cellular compartments, and events such as the activation of a protein by cleavage of one or more of its peptide bonds. Individual events can be grouped together into pathways.
Physical entities can be small molecules like glucose or ATP, or large molecules like DNA, RNA, and proteins, encoded directly or indirectly in the human genome. Physical entities are cross-referenced to relevant external databases, such as UniProt for proteins and ChEBI for small molecules. Localization of molecules to subcellular compartments is a key feature of the regulation of human biological processes, so molecules in the Reactome database are associated with specific locations. Thus in Reactome instances of the same chemical entity in different locations (e.g., extracellular glucose and cytosolic glucose) are treated as distinct chemical entities.
The Gene Ontology controlled vocabularies are used to describe the subcellular locations of molecules and reactions, molecular functions, and the larger biological processes that a specific reaction is part of.
The database contains curated annotations that cover a diverse set of topics in molecular and cellular biology. Details of current and future annotation projects can be found in the calendar of annotation projects
Topics of annotation include;
The database can be browsed and searched as an on-line textbook. An on-line users' guide is available. Users can also download the current data set or individual pathways and reactions in a variety of formats including PDF, BioPAX, and SBML.