title: Inactivation of secretory phospholipase A2 by ionizing radiation.
abstract: The extracellular phospholipase A2s (PLA2) from cobra venom, rattlesnake venom, and porcine pancreas were analyzed by radiation inactivation to determine their functional aggregation states. The analysis was performed in the presence of the protein transferrin at two different concentrations of PLA2: 5 micrograms/ml. The small size of these proteins necessitated the use of high radiation dosages. The catalytic activity of all samples decreased as a single exponential as a function of radiation dosage, to > 97% inactivation. Target size analysis of these curves yielded sizes corresponding to dimers for all three PLA2s, indicating that all three enzymes exist as dimers or larger aggregates under the conditions studied. An analysis of the amount of intact protein remaining by sodium dodecyl sulphate-polyacrylamide gel electrophoresis showed that the loss of protein also followed a dimeric size for all three PLA2s. The loss of protein as a dimer indicates that transfer of radiation energy is occurring between polypeptides.
authors.affiliation: Department of Chemistry, University of California at San Diego, La Jolla 92093-0601, USA.
authors.forename: L J
authors.initials: LJ
authors.lastname: Reynolds
authors.forename: E S
authors.initials: ES
authors.lastname: Kempner
authors.forename: L L
authors.initials: LL
authors.lastname: Hughes
authors.forename: E A
authors.initials: EA
authors.lastname: Dennis
mesh_terms: D000818:Animals; D003435:Crotalid Venoms; D017839:Crotalus; D004307:Dose-Response Relationship, Radiation; D004546:Elapid Venoms; D017815:Elapidae; D007700:Kinetics; D046911:Macromolecular Substances; D010740:Phospholipases / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000528:radiation effects*; D011839:Radiation, Ionizing; D013045:Species Specificity; D013552:Swine; D014168:Transferrin / Q000494:pharmacology
chemical_list: D003435:Crotalid Venoms; D004546:Elapid Venoms; D046911:Macromolecular Substances; D014168:Transferrin; D010740:Phospholipases