The data in the database is manually curated from the scientific literature, and covers all domains of life.

MetaCyc has extensive information about chemical compounds, reactions, metabolic pathways and enzymes.

MetaCyc includes mini reviews for pathways and enzymes that provide background information as well as relevant literature references.

It also provides extensive data on individual enzymes, describing their subunit structure, cofactors, activators and inhibitors, substrate specificity, and, when available, kinetic constants.

MetaCyc data on metabolites includes chemical structures, predicted Standard energy of formation, and links to external databases.