This superfamily consists of structural domains from hydrolytic enzymes that have an alpha/beta fold. These include: cholinesterases, carboxypeptidases, hydrolases, lipases. The ESTHER database (ESTerases and alpha/beta-Hydrolase Enzymes and Relatives) gathers and annotates all the published information related to gene and protein sequences of this superfamily. Structures and families can be found at: http://bioweb.ensam.inra.fr/ESTHER/allstructure and http://bioweb.ensam.inra.fr/ESTHER/general?what=overallTable.

The core of each enzyme is an alpha/beta-sheet (rather than a barrel), containing 8 strands connected by helices. The enzymes are believed to have diverged from a common ancestor, preserving the arrangement of the catalytic residues. All have a catalytic triad, the elements of which are borne on loops, which are the best conserved structural features of the fold. These enzymes have diverged from a common ancestor so as to preserve the arrangement of the catalytic residues, not the binding site. In most of the superfamily members the beta-strands are parallels, but some have an inversion of the first strands, which gives it an antiparallel orientation. The catalytic triad residues are presented on loops. One of these is the nucleophile elbow and is the most conserved feature of the fold. Some other members lack one or all of the catalytic residues. Some members are therefore inactive but others are involved in surface recognition.

Pfam clan [PfamClan:CL0028], Pfam family PFAM:PF00561, INTERPRO:IPR029058,PMID:1409539,PMID:14681380