Do you use pathways databases? Check out the NCBI BioSystems database.
BioSystems can be searched directly or accessed via links from other NCBI databases such as Entrez Gene, PubMed, PubChem Compound, and Protein.
Use BioSystems to list the genes, protein, and small molecules that are involved in a biological pathway; find the pathway in which a given gene or protein or specific small molecule is involved; retrieve 3D structures for proteins involved in a biosystem.