Reactome is a free online database of biological pathways. There are several Reactomes that concentrate on specific organisms, the largest of these is focused on human biology, the following description concentrates on the human Reactome. It is authored by expert biologists, in collaboration with Reactome editorial staff who are all PhD level biologists. Content is cross-referenced to many bioinformatics databases. The rationale behind Reactome is to visually represent biological pathways in full mechanistic detail, while making the source data available in a computationally accessible format. The website can be used to browse pathways and submit data to a suite of data analysis tools. The underlying data is fully downloadable in a number of standard formats including pdf, SBML and Biopax. Pathway diagrams use a Systems Biology Graphical Notation (SBGN)-based style.
The core unit of the Reactome data model is the reaction. Entities (nucleic acids, proteins, complexes and small molecules) participating in reactions form a network of biological interactions and are grouped into pathways. Examples of biological pathways in Reactome include signaling, innate and acquired immune function, transcriptional regulation, translation, apoptosis and classical intermediary metabolism.
The pathways represented in Reactome are species-specific, with each pathway step supported by literature citations that contain an experimental verification of the process represented. If no experimental verification using human reagents exists, pathways may contain steps manually inferred from non-human experimental details, but only if an expert biologist, named as Author of the pathway, and a second biologist, names as reviewer, agree that this is a valid inference to make. The human pathways are used to computationally generate by an orthology-based process derived pathways in other organisms.