simply representing the membership to a molecular system. This representation is used when the detail of the molecular system is not known (KEGG DISEASE) or when a tighter functional unit is indicated within the molecular network (KEGG MODULE). The hierarchical list in KEGG BRITE represents hierarchically organized membership information, which may be called ontology. It is used to represent our knowledge on functional hierarchies inherent in various types of biological systems; not only molecular systems, but also cellular and organismal systems. The content of KEGG BRITE is currently classified into: genes and proteins; compounds and reactions; drugs and diseases; and cells and organisms.
