DegQ could degrade transiently denatured and unfolded proteins which accumulate in the periplasm following stress conditions. DegQ is efficient with Val-Xaa and Ile-Xaa peptide bonds, suggesting a preference for a beta-branched side chain amino acids. Only unfolded proteins devoid of disulfide bonds appear capable to be cleaved, thereby preventing non-specific proteolysis of folded proteins. DegQ can substitute for the periplasmic protease DegP. Acts on substrates that are at least partially unfolded. The cleavage site P1 residue is normally between a pair of hydrophobic residues, such as Val-|-Val. Inhibited by diisopropylfluorophosphate (DFP). Optimum pH is 5.5. The degradation is efficient at pH values between 4.5 and 6. DegQ can reversibly switch between different oligomeric forms that represent inactive (6-mer) and active (12- and 24-mer) protease states. Substrate binding triggers the conversion of the resting DegQ trimer and hexamer into catalytically active 12- and 24-mers. The conversion of 6-mer (DegQ6) into 12-mer (DegQ12) or 24-mer (DegQ24) is crucial in regulating protease activity. Belongs to the peptidase S1C family.