An exotoxin is a soluble chemical excreted by a microorganism, including bacteria, fungi, algae, and protozoa. This is a type of toxin that is produced by bacteria and released into the bloodstream. These toxins can cause damage in the body by destroying cells or disrupting normal cellular metabolism.

There are three main types of exotoxins:

• toxins that act upon the extracellular matrix or connective tissue - this allows the further spread of bacteria and therefore the infection deeper into tissue regions.

  Examples are protease, endopeptidase.

• A-B type toxins - the 'B'-subunit attaches to target regions on cell membranes, the 'A'-subunit tends to have an enzymatic function and enters through the membrane affecting the internal bio-mechanisms. Many toxins are classified as 'AB5' meaning that they contain one enzymatically active A-subunit and a pentamer of five identical B-subunits.

  Toxins of this type include cholera toxin, pertussis toxin, shiga toxin and heat-labile enterotoxin from E. coli.

• Membrane damaging toxins - these toxins are designed primarily to puncture and disrupt the cellular membrane killing cells, a significant resulting example is that of Gangrene.

See also

• Endotoxin

Ektotoxin | Егзотоксин