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Peptidase M4 family including thermolysin, protealysin, aureolysin, and neutral protease This peptidase M4 family includes several endopeptidases such as thermolysin (EC 3.4.24.27), aureolysin (the extracellular metalloproteinase from Staphylococcus aureus), neutral protease from Bacillus cereus, protealysin, and bacillolysin (EC 3.4.24.28). Typically, the M4 peptidases consist of a presequence (signal sequence), a propeptide sequence, and a peptidase unit. The presequence is cleaved off during export while the propeptide has inhibitory and chaperone functions and facilitates folding. The propeptide remains attached until the peptidase is secreted and can be safely activated. All peptidases in this family bind a single catalytic zinc ion which is tetrahedrally co-ordinated by three amino acid ligands and a water molecule that forms the nucleophile on activation during catalysis. The active site is found between two sub-domains; the N-terminal domain contains the HEXXH zinc-binding motif while the helical C-terminal domain, which is unique for the family, carries the third zinc ligand. These peptidases are secreted eubacterial endopeptidases from Gram-positive or Gram-negative sources that degrade extracellular proteins and peptides for bacterial nutrition. They are selectively inhibited by Steptomyces metalloproteinase inhibitor (SMPI) as well as by phosphoramidon from Streptomyces tanashiensis. A large number of these enzymes are implicated as key factors in the pathogenesis of various diseases, including gastritis, peptic ulcer, gastric carcinoma, cholera and several types of bacterial infections, and are therefore important drug targets. Some enzymes of the family can function at extremes of temperatures, while some function in organic solvents, thus rendering them novel targets for biotechnological applications. Thermolysin is widely used as a nonspecific protease to obtain fragments for peptide sequencing. It has also been used in production of the artificial sweetener aspartame. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",