BRENDA is the main collection of enzyme functional data available to the scientific community worldwide. The enzymes are classified according to the Enzyme Commission list of enzymes. It is available free of charge for via the internet (http://www.brenda-enzymes.org/) and as an in-house database for commercial users (requests to our distributor Biobase). The enzymes are classified according to the Enzyme Commission list of enzymes. Some 5000 "different" enzymes are covered. Frequently enzymes with very different properties are included under the same EC number. BRENDA includes biochemical and molecular information on classification, nomenclature, reaction, specificity, functional parameters, occurrence, enzyme structure, application, engineering, stability, disease, isolation, and preparation. The database also provides additional information on ligands, which function as natural or in vitro substrates/products, inhibitors, activating compounds, cofactors, bound metals, and other attributes.