title: Purification and characterization of phosphodiesterase (exonuclease) from Cerastes cerastes (Egyptian sand viper) venom.
abstract: A venom exonuclease 'phosphodiesterase' (E.C. 3.1.4.1) has been purified from Cerastes cerastes venom by a combination of gel filtration on Sephadex G-100 superfine and ion exchange chromatography on DEAE-Sepharose. The enzyme showed a single band on PAGE and SDS-PAGE and had a molecular weight of 110,000. The final preparation was purified 28 fold. It had no carbohydrate and it did not have protease or 5'-nucleotidase activities. Optimum temperature for enzyme activity was 56 degrees C. The enzyme was rapidly inactivated when pre-incubated above 40 degrees C. Energy of activation (Ea) was calculated to be 0.913. The optimum pH was 9.0. Cysteine, glutathione, dithiothreitol, 2-mercaptoethanol, ADP and AMP inhibited the enzyme. Cysteine caused a non-competitive inhibition, while ADP showed a competitive inhibition. EDTA at a concentration of 0.5 mM caused complete inhibition of the enzyme, which could be reversed by the addition of Ca2+ or Mn2+.
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Ain Shams University, Cairo, Egypt.
authors.forename: H Y
authors.initials: HY
authors.lastname: Halim
authors.forename: E A
authors.initials: EA
authors.lastname: Shaban
authors.forename: M M
authors.initials: MM
authors.lastname: Hagag
authors.forename: E W
authors.initials: EW
authors.lastname: Daoud
authors.forename: M F
authors.initials: MF
authors.lastname: el-Asmar
mesh_terms: D000818:Animals; D002241:Carbohydrates / Q000032:analysis; D004534:Egypt; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008970:Molecular Weight; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010727:Phosphoric Diester Hydrolases / Q000032:analysis / Q000302:isolation & purification*; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014757:Viper Venoms / Q000032:analysis*
chemical_list: D002241:Carbohydrates; D010726:Phosphodiesterase Inhibitors; D014757:Viper Venoms; D010727:Phosphoric Diester Hydrolases