Elements of the conserved catalytic structural core are involved in ligand binding in 28 ABH fold enzyme families.

In ligand-bound represenative structures, the recognized substrate molecule (Ligand) frequently interacts with residues that belong to the conserved structural organizations of the ABH fold, including the oxyanion zone (Oxyanion zone), the nucleophile zone (Nucleophile zone), the C-terminal end of strand β6 (Strand β6) and the catalytic acid zone (Catalytic acid zone); residues from the loop that accommodates the catalytic histidine (Catalytic base loop) can also participate in ligand binding. Two ABH fold enzyme families (SCOP family #15 and SCOP family #18) are represented by two structures, each bound to a different substrate, while one ABH fold enzyme family (SCOP family #12) is represented by three representative structures that are bound to three different substrates. The first entry is for carboxylesterase SshEstI (SCOP family #2, PDB ID:3WJ1_A). Residues that are in bold signify that the specific residue does not belong to the conserved catalytic core, but are adjacent to it. Fields of the table that contain the entry “None” indicate that the corresponding geometry does not participate in ligand binding.