A number of prokaryotic proteases have been shown [1,2] to be evolutionary
related; their catalytic activity is provided by a charge relay system similar
to that of the trypsin family of serine proteases but which probably evolved
by independent convergent evolution. The sequence around the residues involved
in the catalytic triad (aspartic acid, serine and histidine) are completely
different from that of the analogous residues in the trypsin serine proteases
and can be used as signatures specific to that category of proteases. The
proteases which are known to belong to this family are listed below.
Staphylococcus aureus V8 proteinase, which preferentially cleaves peptide
bonds on the carboxyl-terminal side of aspartate and glutamate and which is
widely used in protein sequencing studies.
Bacillus licheniformis glutamate specific endopeptidase (GSE) , which
like V8 cleaves on the carboxyl-terminal side of acidic residues, but with
a strong preference for glutamate.
Staphylococcus aureus exfoliative (or epidermolytic) toxins A (gene eta)
and B (gene etb). These toxins cause impetigous diseases commonly referred
to as staphylococcal scalded skin syndrome (SSSS) and have been shown 
to possess proteolytic activity.
These proteins belong to family S2B in the classification of peptidases
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