EFFECTS OF TEMPERATURE AND GLYCERIDES ON THE ENHANCEMENT OF AGKISTRODON PISCIVORUS PISCIVORUS PHOSPHOLIPASE A(2) ACTIVITY BY LYSOLECITHIN AND PALMITIC ACID
Jd. Bell et al., EFFECTS OF TEMPERATURE AND GLYCERIDES ON THE ENHANCEMENT OF AGKISTRODON PISCIVORUS PISCIVORUS PHOSPHOLIPASE A(2) ACTIVITY BY LYSOLECITHIN AND PALMITIC ACID, Biochemistry, 34(36), 1995, pp. 11551-11560
The effect of temperature and various glycerides to modulate the abili
ty of lysolecithin and fatty acid to promote high phospholipase A(2) a
ctivity was studied using dipalmitoylphosphatidylcholine large unilame
llar vesicles as substrate. The length of the lag phase prior to the a
ccumulation of sufficient hydrolysis products (lysolecithin and fatty
acid) to support high phospholipase activity was shortest at temperatu
res near the thermotropic phase transition of the phospholipid substra
te. A reduction in the lag phase correlated with a reduction in the re
quirement for hydrolysis products at the phase transition temperature,
where the bilayer exists in a state of fluctuating domains of gel and
liquid crystal. Dipalmitoylglycerol and tripalmitoylglycerol also red
uced the length of the lag phase. This reduction was both concentratio
n-dependent and temperature-dependent relative to the phase transition
in the presence of the glycerides. As with the effect of temperature,
the ability of di- and triglycerides to decrease the lag time correla
ted with a decrease in the amount of reaction products necessary to pr
omote high phospholipase activity. This effect coincided with the tend
ency of the glycerides to form domains in the bilayer. Glycerides that
did not form domains either had no effect (monopalmitoylglycerol) or
increased the length of the lag phase (dicaprylglycerol). These data s
uggest that the effect of the reaction products to increase phospholip
ase A(2) activity is aided by the presence of fluctuations in lipid do
mains within the bilayer.