Staphopain A (Staphylococcus aureus)
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| Staphopain A | |||||||||
|---|---|---|---|---|---|---|---|---|---|
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| Identifiers | |||||||||
| EC no. | 3.4.22.48 | ||||||||
| CAS no. | 347841-89-8 | ||||||||
| Databases | |||||||||
| IntEnz | IntEnz view | ||||||||
| BRENDA | BRENDA entry | ||||||||
| ExPASy | NiceZyme view | ||||||||
| KEGG | KEGG entry | ||||||||
| MetaCyc | metabolic pathway | ||||||||
| PRIAM | profile | ||||||||
| PDB structures | RCSB PDB PDBe PDBsum | ||||||||
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Staphopain A (EC 3.4.22.48, ScpA, ScpAaur, staphylopain A, staphylococcal cysteine proteinase) is a secreted cysteine protease produced by Staphylococcus aureus. It was first identified in the S. aureus V8 strain as a papain-like cysteine protease. The protease distinguishes itself from the other major proteases of S. aureus in its very broad specificity and its ability to degrade elastin.[1][2]
Staphopain A expressed from the gene scpA within the scp operon. The operon also contains the gene scpB for staphostatin A (specific inhibitor of staphopain A), downstream of scpA.[3][4]
Staphopain A is largely co-expressed with the other three major proteases of S. aureus: aureolysin, glutamyl endopeptidase, and staphopain B. The transcription of scp occurs via a promoter controlled by "housekeeping" sigma factor σA and up-regulated by accessory gene regulator agr. It is at also repressed by staphylococcal accessory regulator sarA and by alternative sigma factor σB (a stress response modulator of Gram-positive bacteria). ssp expression is highly expressed in post-exponential growth phase.[4] A more complex network of modulators and of environmental conditions affecting ssp expression have been suggested, however. Up-regulation of aureolysin during phagocytosis have also been observed.[5][6]
The scpA gene has a high prevalence in the genome of both commensal- and pathogenic-type S. aureus strains.[7]
Activation and inhibition
Staphopain A is expressed as an inactive zymogen. In contrast to the other proteases, however, it appears to undergo rapid autocatalytic activation. It is thus also independent of the activation cascade of the three other proteases.[4][8]
S. aureus expresses the intracellular inhibitor staphostatin A, specific against staphopain A. As the activation of staphopain A could occur before it has been secreted by the bacteria, the staphostatin acts as prevention against harmful intracellular activity of the protease.[3][8][9]
