Dermonecrotic toxins cleave the phosphodiester linkage between the phosphate and headgroup of certain phospholipids (sphingolipid and lysolipid substrates), forming an alcohol (often choline) and a cyclic phosphate (By similarity). This toxin acts on sphingomyelin (SM) (By similarity). It may also act on ceramide phosphoethanolamine (CPE), lysophosphatidylcholine (LPC) and lysophosphatidylethanolamine (LPE), but not on lysophosphatidylserine (LPS), and lysophosphatidylglycerol (LPG) (By similarity). It acts by transphosphatidylation, releasing exclusively cyclic phosphate products as second products (By similarity). Induces dermonecrosis, hemolysis, increased vascular permeability, edema, inflammatory response, and platelet aggregation (By similarity). an N-(acyl)-sphingosylphosphocholine = an N-(acyl)-sphingosyl-1,3-cyclic phosphate + choline an N-(acyl)-sphingosylphosphoethanolamine = an N-(acyl)-sphingosyl-1,3-cyclic phosphate + ethanolamine a 1-acyl-sn-glycero-3-phosphocholine = a 1-acyl-sn-glycero-2,3-cyclic phosphate + choline a 1-acyl-sn-glycero-3-phosphoethanolamine = a 1-acyl-sn-glycero-2,3-cyclic phosphate + ethanolamine Binds 1 Mg(2+) ion per subunit. Expressed by the venom gland. Belongs to the arthropod phospholipase D family. Class I subfamily. The lack of peptide signal and first catalytic site is due to the cloning strategy (the sequence was amplified from the second ATG codon). The functional tests have been done using an incomplete recombinant protein resulting in an inactive protein. However, this functionally inactive recombinant protein behaved as a good immunogen, capable of inducing immunoprotection in test animals. The most common activity assay for dermonecrotic toxins detects enzymatic activity by monitoring choline release from substrate. Liberation of choline from sphingomyelin (SM) or lysophosphatidylcholine (LPC) is commonly assumed to result from substrate hydrolysis, giving either ceramide-1-phosphate (C1P) or lysophosphatidic acid (LPA), respectively, as a second product. However, two studies from Lajoie and colleagues (2013 and 2015) report the observation of exclusive formation of cyclic phosphate products as second products, resulting from intramolecular transphosphatidylation. Cyclic phosphates have vastly different biological properties from their monoester counterparts, and they may be relevant to the pathology of brown spider envenomation.