R. Haftendorn et al. / Chemistry and Physics of Lipids 104 (2000) 57–66
65
Acknowledgements
length of the acyl chains can be observed. Short
chain 1,3-PCs (C8 and C10) are more effective as
inhibitors than the long-chain 1,3-PCs (C14, C16,
and C18). This tendency is opposite to the in-
hibitory effects of the alkyl phosphocholines
(Table 2), which have been studied recently
(Dittrich et al., 1996). Interestingly, the maxi-
mum inhibition effects are much larger with the
one-chain alkyl phosphocholines than with the
glycerol derivatives. The different organisation
of the substrate aggregates containing inhibitor
and detergent molecules and/or the different
affinities of the inhibitor molecules to the PLD
might be reasons for this behaviour. With both
types of inhibitors the inhibitory effect decreases
with increasing substrate concentration. There-
fore, a competitive type of inhibition is sug-
gested although a classical kinetic analysis is not
possible because of the sigmoidal curves of ini-
tial rates versus substrate concentration (Dittrich
et al., 1998). Further studies are necessary to
elucidate the inhibition mechanism.
The financial support by the Ministerium des
Landes Sachsen-Anhalt is gratefully acknowl-
edged. The authors also wish to thank Yvonne
Markert for the determination of the cmc-values
of the 1,3-PCs, and Gerd Scherer for performing
the NMR spectra.
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