Members of this family have serine hydrolase activity. They contain a conserved serine hydrolase motif, GXSXG/A, where the serine is a putative nucleophile. This family has an alpha-beta hydrolase fold. Eukaryotic members of this family have a conserved LXCXE motif, which binds to retinoblastomas. This motif is absent from prokaryotic members of this family.