The EXTRACELLULAR ENZYMES PRODUCED BY S. AUREUS include:
- Catalase: Catalase is an enzyme produced by pathogenic aureus, and it inhibits the process of phagocytosis. It enhances the survival of the pathogen in phagocytes through the production of the enzyme. Catalase enzyme production is used for the biochemical identification of S. aureus in the laboratory, and it converts hydrogen peroxide (H2O2) to water and oxygen; thereby walling off or protecting the infected body sites from phagocytic cells.
- Proteases: Proteases or proteinases are extracellular enzymes produced by pathogenic aureus, and which assist the pathogen in breaking down protein molecules.
- Nuclease: Nuclease enzymes produced by pathogenic aureus breaks down nucleic acids of infected cells in human host. DNase enzymes produced by pathogenic S. aureus perform a similar function with nucleases in that they destroy the host cell DNA.
- Beta-lactamase: Beta lactamase enzymes produced by pathogenic aureus are of clinical significance in that this class of enzymes confers on the pathogen the capacity to develop resistance to a range of synthetic antibiotics and other antimicrobials. Beta lactamase enzymes of pathogenic S. aureus degrade beta-lactam antibiotics such as penicillins.
- Lipase: Lipases are fat or lipid destroying enzymes produced by pathogenic aureus.
- Coagulase: Pathogenic aureus produces coagulase enzymes, and this characteristic differentiates them from non-pathogenic S. aureus strains which do not produce coagulase. The production of this enzyme by pathogenic S. aureus strains inhibits the process of phagocytosis in the affected human host cells. Coagulase enzymes converts fibrinogen to fibrin clot which surrounds and protect infected sites from the action of phagocytes. The production of coagulase (blood clotting factor) is used to identify pathogenic S. aureus in the clinical microbiology laboratory.
- Staphylokinase: Staphylokinase is an extracellular enzyme produced by pathogenic aureus, and it is a plasminogen activator (i.e. the enzyme stimulates a plasmin-like proteolytic activity that lyses fibrin). Streptokinase may aid in the spreading of the pathogen within the host due to its ability to degrade fibrin clots.
- Hyaluronidase: Hyaluronidase is an enzyme that breaks down hyaluronic acid that makes up the host connective tissues. The ability of pathogenic aureus to produce hyaluronidase encourages the spread of the pathogen in host tissues.
- Protein A: Protein A is found in the cell wall of most aureus strains, and they prevent the activation of complement in the host cell. Anti-phagocytic in nature, protein A binds to the crystallizable fragment (Fc portion) of antibody molecules (e.g. IgG), and thus prevents phagocytosis and opsonization. In this way, protein A (staphylococcal surface protein) contributes to the virulence of pathogenic S. aureus.