Biochemistry and pharmacology of the crotoxin complex

Summary

• 1. Crotoxin, the crystallizable, proteinaceous, approximately electroneutral fraction from the venom ofCrotalus durissus terrificus, has been resolved further by chromatography on carboxymethyl cellulose. We obtained:

• a) A basic phospholipase A with comparatively low toxicity in mice (LD₅₀ i.v. 0.54 mg/kg; LD₅₀ s.c. > 100 mg/kg), whereas the toxicity of crotoxin was 0.108 mg/kg i.v. and 0.50 mg/kg s.o., respectively. In contrast, the specific enzymatic activity of phospholipase A was about 4 times higher than in crotoxin, depending on the dosage used. Overall recovery of activity was 140% to 170%, which suggests the removal of an inhibitor.

• b) An acidic substance (“Crotapotin”)1 devoid of toxicity (LD⁵⁰ i.v. > 50 mg/kg, mice) and phospholipase activity.

• c) A mixture (called fraction III) of phospholipase A, crotapotin and a third basic substance. The latter, being inactive in our tests, is present in small amounts only (about 1% of crotoxin).

• 2. Recombination of crotapotin with phospholipase A increases the i.v. toxicity of phospholipase A approximately 12 fold to 0.042 mg/kg; the s.c. toxicity of the enzyme is raised approximately 1000 fold to 0.13 mg/kg.

• 3. In contrast to potentiating the phospholipase toxicity, crotapotin strongly inhibits the enzymatic activity in vitro.

• 4. These findings help in explaining the former reports on the chemical heterogeneity of crotoxin and on the preparation of toxic compounds with low phospholipase activity from it. Crotoxin is to be considered as a complex consisting of phospholipase A, crotapotin, and small amounts of impurities.