title: Inhibition of Naja nigricolis venom acidic phospholipase A2 catalysed hydrolysis of ghost red blood cells by columbin.
abstract: The inhibitory effects of a naturally occurring diterpenoid furanolactone, columbin, on partially purified acidic phospholipase A2 (PLA2) from Naja nigricolis was investigated. Columbin inhibited the N. nigricolis PLA2 in a dose related pattern with an IC50 value of 2.5 microM. Double reciprocal plots of initial velocity data of inhibition by columbin revealed a non-competitive pattern. The KM remained constant at 19 microM, while the Vmax changed from 54 micromoles/min/mg to 32 micromoles/min/mg and 20 micromoles/min/mg in the presence of 2 and 10 microM of columbin, respectively. Extrapolated Ki values were 3 and 6.28 microM at 2 and 10 microM inhibitor, respectively. Columbin also inhibited PLA2 hydrolysis of ghost RBC in a dose-dependent fashion. At least 70% suppression of PLA2-catalysed haemolysis of RBC was observed in the presence of 2 microM columbin.
mesh_terms: D000818:Animals; D002384:Catalysis / Q000187:drug effects; D004224:Diterpenes / Q000494:pharmacology*; D004546:Elapid Venoms / Q000037:antagonists & inhibitors* / Q000201:enzymology; D004912:Erythrocytes / Q000378:metabolism*; D006461:Hemolysis / Q000187:drug effects; D006868:Hydrolysis / Q000187:drug effects; D007700:Kinetics; D007783:Lactones / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000378:metabolism; D010741:Phospholipases A / Q000037:antagonists & inhibitors*; D054467:Phospholipases A2; D051381:Rats
chemical_list: D004224:Diterpenes; D004546:Elapid Venoms; D007783:Lactones; D010713:Phosphatidylcholines; D010741:Phospholipases A; D054467:Phospholipases A2; C062514:columbin