This family of bacteria aspartate proteases is a subfamily of retropepsin-like protease family, which includes enzymes from retrovirus and retrotransposons. While fungal and mammalian pepsin-like aspartate proteases are bilobal proteins with structurally related N- and C-termini, this family of bacteria aspartate proteases is half as long as their fungal and mammalian counterparts. The monomers are structurally related to one lobe of the pepsin molecule and function as homodimers. The active site aspartate occurs within a motif (Asp-Thr/Ser-Gly), as it does in pepsin. In aspartate peptidases, Asp residues are ligands of an activated water molecule in all examples where catalytic residues have been identified. This group of aspartate proteases is classified by MEROPS as the peptidase family A2 (retropepsin family, clan AA), subfamily A2A.