Specifically inhibits the cysteine protease staphopain B (SspB) by blocking the active site of the enzyme. Probably required to protect cytoplasmic proteins from being degraded by prematurely activated/folded prostaphopain B. Also involved in growth capacity, viability and bacterial morphology. Forms a stable non-covalent complex with prematurely activated/folded SspB. Expression occurs in a growth-phase-dependent manner with optimal expression at post-exponential phase. Up-regulated by Agr (accessory gene regulator) and repressed by SarA (staphylococcal accessory regulator) and sigmaB factor. Inactivated by staphylococcal serine protease (SspA). Disruption of sspC causes a total loss of secreted extracellular proteins and a partial loss of peptidoglycan-associated proteins. Loss of SspC results in profoundly reduced susceptibility of peptidoglycan to lysis by lysostaphin. Belongs to the protease inhibitor I57 (SspC) family.