title: D-dihexanoylphosphatidylcholine is not a pure competitive inhibitor of phospholipase A2 hydrolysis of L-dihexanoylphosphatidylcholine.
abstract: The inhibition of Crotalus adamanteus phospholipase A2 hydrolysis of L-dihexanoylphosphatidylcholine by D-dihexanoylphosphatidylcholine was investigated with inhibitor and substrate in the monomeric concentration range. The results showed that the D-enantiomer acts as a partial (not pure) competitive inhibitor of the enzyme. These results suggest that an ESI complex exists, in which hydrolysis of the substrate still occurs. Thus, binding of the D-enantiomer to the enzyme decreases the affinity for the substrate by a factor, alpha, while Vmax is unaffected. The value of alpha was determined to be 4.70 +/- 0.14. These findings complicate the use of D-phosphatidylcholines in mixed micelles with the L-enantiomer as a possible method to investigate the mechanism of interfacial activation of this enzyme.
mesh_terms: D003435:Crotalid Venoms / Q000032:analysis; D006868:Hydrolysis; D007700:Kinetics; D010713:Phosphatidylcholines / Q000378:metabolism / Q000494:pharmacology*; D010740:Phospholipases / Q000037:antagonists & inhibitors*; D010741:Phospholipases A / Q000037:antagonists & inhibitors*; D054467:Phospholipases A2; D013237:Stereoisomerism
chemical_list: D003435:Crotalid Venoms; D010713:Phosphatidylcholines; C032166:1,2-hexanoylphosphatidylcholine; D010740:Phospholipases; D010741:Phospholipases A; D054467:Phospholipases A2