Reactome is centered on the molecular functions of human proteins. When possible, we annotate these functions with published evidence from work with human systems. When such evidence isn’t available, but the function is known to be well conserved across species and experimental evidence exists for a non-human species, we annotate the reaction for the protein in that species and manually infer the reaction involving the homologous human protein.

We also computationally infer reactions for a small group of model organisms from our manually annotated human data. This group of organisms is centered on organisms of interest to the Alliance for Genome Resources. The process for these computationally inferred events is here.

In a collaborative project, the Reactome data model has been adopted by Plant Reactome to capture pathway information for diverse species of plants, including crop plants.