EC Tree

A hierarchical classification tree of enzymes constructed based on the IUBMB Enzyme Commission (EC) numbering system. The EC system employs a four-level numerical code (a.b.c.d) corresponding to the enzyme's main class, subclass, sub-subclass, and specific catalytic reaction; this tree is organized according to the type of chemical reaction catalyzed, rather than protein sequence homology. Enzyme databases such as BRENDA and ExPASy-ENZYME offer EC tree browsing capabilities, allowing users to search and explore all cataloged enzyme entries level by level.