prototoxinn.
/ˈprəʊtə(ʊ)ˌtɒksɪn/, U.S. /ˈproʊdoʊˌtɑks(ə)n/ Medicine.
1. A (hypothetical) component of diphtheria toxin that has the greatest toxicity and highest affinity for antitoxin. Now disused.
ΚΠ
1900 W. A. N. Dorland Amer. Illustr. Med. Dict. 541 Prototoxin, any one of the first of the four groups of diphtheria-toxins.
1904 Brit. Med. Jrnl. 10 Sept. 567 We have three different toxins with different toxicity and different avidities to the antitoxin, viz. the prototoxin, the deuterotoxin, and the tritotoxin.
2. An inactive (non-toxic) precursor of a toxin, esp. of the epsilon toxin of the pathogenic bacterium Clostridium perfringens.
ΚΠ
1954 Amer. Jrnl. Vet. Res. 15 361/1 This toxin [of type D Clostridium perfringens] is not produced as such by the bacteria but, rather, as a relatively inactive prototoxin which is converted into the active toxin by digestion with proteolytic enzymes.
1962 Nature 6 Jan. 69/2 Verwoerd obtained crystalline prototoxin of ε-antigen by methanol fractionation, but the yields were too small for further investigation.
2004 Anaerobe 10 145/2 Enzymatic activation increases the toxicity of epsilon toxin at least 1000-fold over the..prototoxin.
This entry has been updated (OED Third Edition, September 2007; most recently modified version published online March 2022).
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n.1900