Putative pseudoenzymes have been predicted within 252 CATH superfamilies. Functional families with zero EC terms (and zero GO terms describing catalytic activity) were identified within enzyme CATH superfamilies with experimentally-validated catalytic domains, suggesting that these families are very likely to be potential pseudoenzymes. Please note that these predictions will need to be experimentally validated to confirm that they are indeed pseudoenzymes.

The CATH database is a hierarchical domain classification of protein structures in the Protein Data Bank. Protein structures are classified using a combination of automated and manual procedures. There are four major levels in this hierarchy:

• Class - structures are classified according to their secondary structure composition (mostly alpha, mostly beta, mixed alpha/beta or few secondary structures).
• Architecture - structures are classified according to their overall shape as determined by the orientations of the secondary structures in 3D space but ignores the connectivity between them.
• Topology (fold family) - structures are grouped into fold groups at this level depending on both the overall shape and connectivity of the secondary structures.
• Homologous superfamily - this level groups together protein domains which are thought to share a common ancestor and can therefore be described as homologous.

Each level of the hierarchy is given a numeric identifier so the identifier for a superfamily would look like "C.A.T.H" (eg. "1.10.10.10" is the identifier for the CATH superfamily "Winged helix-like DNA-binding domain superfamily")