Enzymatic characterization of the major phospholipase A2 component of sea anemone (Aiptasia pallida) nematocyst venom.
The purified beta phospholipase A2 (PLA2; EC 3.1.1.4) (PLA2) from sea anemone (Aiptasia pallida) nematocysts is larger and more labile than other known venom PLA2s. In common with all other known venoms and most secretory PLA2s, the beta PLA2 requires mM Ca2+ for optimal activity and is surface-activated by aggregated lipids such as mixed micelles of detergent and phospholipid. The beta PLA2 exhibits an unusually steep and narrow pH optimum of activity at pH 7.7. The effects of changes in pH on the activity of the enzyme suggest that the active site contains functional groups having a pKs of about 7.0 and 8.0. The effects of temperature on beta PLA2 activity show a marked decrease in the energy of activation above the pre-transition temperature, suggesting that the enzyme "melts" both fatty chains in order for catalysis to occur.
Grotendorst
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GR
Department of Cell Biology and Anatomy, University of Miami School of Medicine, FL 33136, USA.
Hessinger
D A
DA
D000818:Animals; D002413:Cations, Divalent / Q000494:pharmacology; D003064:Cnidarian Venoms / Q000201:enzymology* / Q000494:pharmacology; D004355:Drug Stability; D006461:Hemolysis / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D010741:Phospholipases A / Q000737:chemistry* / Q000187:drug effects / Q000302:isolation & purification* / Q000378:metabolism; D054467:Phospholipases A2; D012615:Sea Anemones; D013696:Temperature
D002413:Cations, Divalent; D003064:Cnidarian Venoms; D010741:Phospholipases A; D054467:Phospholipases A2