Staphylococcus aureus remains one of the major human pathogens, causing a number of diverse infections. The growing antibiotic resistance, including vancomycin and methicilin‑resistant strains raises the special interest in virulence mechanism of this pathogen. Among a number of extracellular virulence factors, S. aureus secretes several proteases of three catalytic classes—metallo, serine and papain‑like cysteine proteases. The expression of proteolytic enzymes is strictly controlled by global regulators of virulence factors expression agr and sar and proteases take a role in a phenotype change in postlogarithmic phase of growth. The staphylococcal proteases are secreted as proenzymes and undergo activation in a cascade manner.
Staphopains, two cysteine, papain‑like proteases of S. aureus are both ~20 kDa proteins that have almost identical three‑dimensional structures, despite sharing limited primary sequence identity. Although staphopain A displays activity similar to cathepsins, recognising hydrophobic residues at P2 position and large charged residues at P1, staphopain B differs significantly, showing significant preference towards b‑branched residues at P2 and accepting only small, neutral residues at the P1 position. There is limited data available on the virulence potential of staphopains in in vivo models. However, in vitro experiments have demonstrated a very broad activity of these enzymes, including destruction of connective tissue, disturbance of clotting and kinin systems and direct interaction with host immune cells. Staphopain genes in various staphylococci species are regularly followed by a gene encoding an extremely specific inhibitor of the respective staphopain. This pattern is conserved across species and it is believed that inhibitors (staphostatins) protect the cytoplasm of the cell from premature activation of staphopains during protein folding. Notably, production and activity of staphopains is controlled on each level, from gene expression, through presence of specific inhibitors in cytoplasm, to the cascade‑like activation in extracellular environment. Since these systems are highly conserved, this points to the importance of these proteases in the survival and/or pathogenicity of S. aureus.
Cysteine proteases have been discovered in various bloodfeeding ectoparasites. Here, we assemble the available information about the function of these peptidases and reveal their role in hematophagy and parasite development. While most of the data shed light on key proteolytic events that play...
Cysteine proteases are important for the growth and survival of apicomplexan parasites that infect humans. The apicomplexan Toxoplasma gondii expresses five members of the C1 family of cysteine proteases, including one cathepsin L‑like (TgCPL), one cathepsin B‑like (TgCPB) and three...
Helminth parasites (nematodes, flatworms and cestodes) infect over 1 billion of the world’s population causing high morbidity and mortality. The large tissue‑dwelling worms express papain‑like cysteine peptidases, termed cathepsins that play important roles in virulence including host...
Cruzain is the major papain‑like cysteine protease of Trypanosoma cruzi, the etiological agent causing Chagas’ disease in humans in South America. Cruzain is indispensable for the survival and propagation of this protozoan parasite and therefore, it has attracted considerable interest as a...
A number of cysteine proteases of malaria parasites have been described and many more are suggested by analysis of the Plasmodium falciparum genome sequence. The best characterized of these proteases are the falcipains, a family of four papain‑family enzymes. Falcipain‑2 and falcipain‑3...
The cystatin superfamily comprises several groups of protease inhibitors. In this chapter we will focus on I25 family members, which consist predominantly of the Type 2 cystatins. Recently, a wealth of information on these molecules and their activities has been described. Parasite cystatins...
Trichobilharzia regenti and T. szidati are schistosomes that infect birds. Although T. regenti/T. szidati can only complete their life cycle in specific bird hosts (waterfowl), their larvae—cercariae are able to penetrate, transform and then migrate as schistosomula in nonspecific...
Periodontitis is a disease affecting the supporting structures of the teeth. The most severe forms of the disease result in tooth loss and have recently been strongly associated with systemic diseases, including cardiovascular and lung diseases and cancer. The disease is caused by biofilms of...
Cysteine proteases of the protozoan parasite Entamoeba histolytica are key virulence factors involved in overcoming host defences. These proteases are cathepsin‑like enzymes with a cathepsin‑L like structure, but cathepsin‑B substrate specificity. In the host intestine, amoeba cysteine...
Staphylococcus aureus remains one of the major human pathogens, causing a number of diverse infections. The growing antibiotic resistance, including vancomycin and methicilin‑resistant strains raises the special interest in virulence mechanism of this pathogen. Among a number of...
We review Clan CA Family C1 peptidases of kinetoplastid parasites (Trypanosoma and Leishmania) with respect to biochemical and genetic diversity, genomic organization and stage‑specificity and control of expression. We discuss their contributions to parasite metabolism, virulence and...
In mammals, cysteine proteases are essential for the induction and development of both innate and adaptive immune responses. These proteases play a role in antigen‑ and pathogen‑recognition and elimination, signal processing and cell homeostasis. Many pathogens also secrete cysteine...
Parasitic nematodes express and secrete a variety of proteases which they use for many purposes including the penetration of host tissues, digestion of host protein for nutrients, evasion of host immune responses and for internal processes such as tissue catabolism and apoptosis. For these...