Distribution spectrum of paraoxonase activity in HDL fractions

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.

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.

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.

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