Analysis of the kinetics of phospholipid activation of cobra venom phospholipase A2.

摘要: A kinetic analysis of the "dual phospholipid model" for cobra venom phospholipase A2 (Hendrickson, H. S., and Dennis, E. A. (1984) J. Biol. Chem. 259, 5734-5739) was applied to activation A2-catalyzed hydrolysis a thiol ester analog phosphatidylethanolamine (thio - PE) in Triton X 100/phospholipid mixed micelles by various phosphorylcholine-containing activators. Activation thio-PE didecanoylphosphatidylcholine (PC) found be function surface concentration activator rather than bulk concentration. Its presence did not affect initial binding enzyme micelle as determined kinetically. After surface, appears due enzyme-lipid surface. does appear affinity substrate, but affects catalytic efficiency characterized value Vmax. The monomeric dibutyryl-PC, when used an at 57 mM (bulk concentration), also showed effects dilution with X-100, which would expected unless lipid is incorporated into some extent these high concentrations. phosphatidylcholine, thio-PC, less effective didecanoyl-PC activator, appeared more decylphosphorylcholine. conformational change upon after bound substrate interface, discussed possible mechanism this activation.