Distribution spectrum of paraoxonase activity in HDL fractions.

Background: Paraoxonase (PON1) associated with HDL can be regarded as a cardio- and vasoprotective enzyme. However, because HDL is not a homogeneous fraction, it is important to investigate in which subgroups of HDL active PON1 is located. It would also be useful to determine density profiles of the HDL apolipoproteins (Apo) E and J.

Methods: We investigated the density range of HDL (rho = 1.063-1.256 kg/L) in healthy individuals, using the ultracentrifugation reference method and a newly introduced automated fractionation method. Profiles of PON1 activity and ApoA-I, ApoA-II, ApoE, ApoJ, and cholesterol concentrations were obtained by use of various density gradients.

Results: PON1 activity was highest in the more dense HDL(3) and VHDL fractions where PON1 was not dissociated from the particles during centrifugation. The fraction in density range 1.175-1.185 kg/L showed not only the highest PON1 activity, but also the highest specific activity (activity per HDL particle). This fraction was the least-dense fraction containing both ApoE and ApoJ. Only the Q192R polymorphism had an effect on the distribution profile of PON1 activity. In contrast, L55M and the T(-107)C polymorphisms (determined by a novel nonradioactive method) were without effect on the density distribution of PON1 activity.

Conclusion: The HDL(3) fraction, which is important in reverse cholesterol transport, also carries the highest PON1 activity.