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) with high activity (about 30.5-31.5 U/mg) (PubMed:15450925, PubMed:16759681). 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). Is lethal to mice (PubMed:16759681). 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. LD(50) is 200-250 ug/kg by intraperitoneal injection into mice. Belongs to the arthropod phospholipase D family. Class II subfamily. Class IIa sub-subfamily. 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.