title: Application of enantiomeric 2-sn-phosphatidylcholines in interfacial enzyme kinetics of lipolysis.
abstract: Two enantiomeric 2-sn-phosphatidylcholines containing hexanoyl and dodecanoyl acyl chains have been synthesized, enabling the study of the action of phospholipase A2 (EC 3.1.1.4) at lipid-water interfaces characterized by identical physico-chemical properties. Monolayer kinetics and bulk kinetics in the presence of Triton X-100 micelles were studied but the interpretation of the results is impeded by the fact that interfacial saturation conditions cannot be reached. In contrast, the use of the substrate analog n-tetradecylphosphorylcholine allows the determination of the interfacial kinetic parameters kcat and K*m. Dodecanoic acid is released from the most susceptible isomer about 13 times more rapidly than hexanoic acid from the stereoisomer in spite of the higher K*m of the former. The results are discussed in terms of the particular active site architecture and the possible influence of the "quality of the interface" on the kinetic parameters.
mesh_terms: D001665:Binding Sites; D007700:Kinetics; D008433:Mathematics; D010179:Pancreas / Q000201:enzymology; D010713:Phosphatidylcholines; D010740:Phospholipases / Q000378:metabolism*; D011312:Pressure; D011485:Protein Binding; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D013499:Surface Properties
chemical_list: D010713:Phosphatidylcholines; D010740:Phospholipases