KEGG

KEGG PATHWAY Database records networks of molecular interactions in the cells, and variants of them specific to particular organisms.

Introduction
The KEGG database was initiated by the Japanese human genome programme in 1995 and is part of the Kyoto Encyclopedia of Genes and Genomes. According to the developers they consider KEGG to be a "computer representation" of the biological system. The KEGG database can be utilized for modeling and simulation, browsing and retrieval of data. It is a part of the systems biology approach.

KEGG maintains four main databases
 * KEGG Pathway
 * KEGG Genes
 * KEGG Ligand
 * KEGG BRITE

Databases
KEGG connects known information on molecular interaction networks, such as pathways and complexes (this is the Pathway Database), information about genes and proteins generated by genome projects (including the gene database) and information about biochemical compounds and reactions (including compound and reaction databases). These databases are different networks, known as the protein network, the gene universe and the chemical universe respectively. There are efforts in progress to add to the knowledge of KEGG, including information regarding ortholog clusters in the KO (KEGG Orthology) database. 

KEGG Pathways:


 * Metabolism
 * Genetic Information Processing
 * Environmental Information Processing
 * Cellular Processes
 * Human Diseases
 * Drug Development

Ligand Database:


 * Compound
 * Drug
 * Glycan
 * Reaction
 * RPAIR
 * Enzyme