ATP-dependent Clp protease proteolytic subunit (ClpP) is an enzyme that in humans is encoded by the CLPP gene. This protein is an essential component to form the protein complex of Clp protease (Endopeptidase Clp). In bacteria, it was shown that ClpP is able to cleave full-length proteins without being associated with ClpA but the degradation is at a much slower rate. Fully functional Clp protease requires the participation of AAA+ ATPase. These ClpX chaperons recognize, unfold and transfer protein substrates to proteolytic core formed by ClpP tetradecamer. The proteolytic sites of ClpP subunits contain hydrophobic grooves which recruit substrate and host the catalytic triad Asp-His-Ser. In several bacteria, such as E. coli, proteins tagged with the SsrA peptide (ANDENYALAA) encoded by tmRNA are digested by Clp proteases. Proteases target damaged or misfolded proteins, transcription factors and signaling proteins in bacteria to coordinate complex cell responses and thus they have robust importance for the physiology and virulence of bacteria. In P. aeruginosa, ClpP1 is expressed constitutively throughout growth whereas ClpP2 expression is induced 10-fold in stationary phase. Quorum-sensing transcription factor LasR activates expression of ClpP2 in stationary phase. ClpP1 and ClpP2 have differential cleavage specificities which contributes to total peptidase activity of PaClpP17P27. Peptidase and protease action of PaClpP17P27 produces cleavage products that enhance biofilm formation in P. aeruginosa. The protein encoded by this gene belongs to the peptidase family S14 and hydrolyzes proteins into small peptides in the presence of ATP and magnesium. The protein is transported into mitochondrial matrix and is associated with the inner mitochondrial membrane.