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Pro-Pro endopeptidase (PPEP) and similar proteins; belongs to peptidase family M34 This subfamily includes the enzyme Pro-Pro endopeptidase (PPEP-1, EC 3.4.24.89, also known as Zmp1 (Clostridium difficile-type)), an extracellular metalloprotease showing a unique specificity for hydrolyzing a Pro-Pro bond. It belongs to peptidase family M34 and has the hallmark metalloprotease motif HEXXH, where the two His residues bind a single zinc atom, and the Glu has a catalytic role. PPEP-1 cleaves two C. difficile cell surface proteins (CD2831 and CD3246) involved in adhesion, one of which is encoded by the gene adjacent to the ppep-1 gene. There are multiple PPEP-1 cleavage sites located just above the site of attachment to the peptidoglycan layer. PPEP-1 may play a role in switching from an adhesive to a motile phenotype. Also included in this subfamily is Paenibacillus alvei PPEP-2, a secreted Pro-Pro endopeptidase. The cleavage motif of PPEP-2, PLP PVP, is distinct from that of PPEP-1 (VNP PVP). PPEP-2 cleavage sites in a cell-surface protein, with putative extracellular matrix-binding domains, and encoded by the adjacent gene, suggests a similar role of PPEP-2 in controlling bacterial adhesion. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",