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Enzyme that Damage the Body

Many pathogenic microorganisms produce enzymes that contribute to their ability to invade the infected body, sometimes with destructive consequences. The potentially fatal symptoms of gas gangrene, for example, are largely due to lecithinase, an enzyme produced by the pathogen Clostridium perfrinens. The substrate for this enzyme is lecithin, a component of human cell membranes. Dissolving cell membranes kills host tissue so it no longer presents an effective solid barrier to microbial invasion of surrounding tissues. The pathogen leaves a trail of enzymatically digested tissue as it invades new body sites. Lecithinase production which can be detected by growing the pathogen on egg yolk media has proved to be a valuable laboratory indicator in the diagnosis of gas gangrene.

Enzymes that contribute to the ability of a pathogen to injure people do so by one of two mechanisms: (1) direct destruction of host tissue, as in gas gangrene, or (2) interruption of essential metabolic processes. The pathogen that causes diphtheria, for example, produces a toxic enzyme that inactivates one of the components needed for protein synthesis by host cells. Unable to produce protein, the host cell die, as soon as does the infected owner of those cells if enough of them are impaired.

In addition to directly injuring the host, microbial enzymes may protect the pathogen by inactivating substances that would otherwise eliminate infection. For example, many species of bacteria produce the enzyme penicillinase, which destroys the antibiotic penicillin. The failure of this antibiotic in treating many Staphylococcus aureus infections is common, due to the emergence of penicillinase-producing strains of the bacterium.
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