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Enzymes and Toxins of Pathogenesis - Coggle Diagram
Enzymes and Toxins of Pathogenesis
Enzymes (Exoenzymes)
Help break host tissue and evade immune response
Examples:
Hyaluronidase: Breaks connective tissue
Coagulase (S. aureus): Forms protective fibrin clots
Streptokinase (S. pyogenes): Dissolves clots
Toxins
Exotoxins (Protein Toxins)
Secreted by bacteria, highly specific and potent
Types: Cytolytic (cytotoxins): Lyse cells by disrupting membranes. E.g., S. aureus α-toxin, C. perfringens lecithinase
AB Toxins: A = active subunit; B = binding
Examples: Diphtheria toxin: Inhibits protein synthesis (coded by phage β)
Botulinum toxin (C. botulinum): Blocks acetylcholine → flaccid paralysis
Tetanus toxin (C. tetani): Blocks glycine → spastic paralysis
Cholera toxin (V. cholerae): AB enterotoxin → fluid secretion, diarrhea
Enterotoxins
Target intestine → fluid loss
Examples: Cholera toxin, Shiga-like toxin
Superantigens
Overactivate immune system → toxic shock
Produced by: S. aureus, S. pyogenes
Endotoxins
From LPS (Gram-negative outer membrane), Lipid A is toxic part, Less potent than exotoxins but can cause endotoxic shock, Detected by LAL assay (horseshoe crab blood)
Host Immune Evasion Strategies
Capsules: Prevent phagocytosis (S. pneumoniae)
Proteases: Degrade host antibodies
Mimicry, antigen variation
Biofilms resist immune cell penetration