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Journal of Lipid Research, Vol. 49, 1246-1253, June 2008
Copyright © 2008 by American Society for Biochemistry and Molecular Biology

HDL subfraction distribution of paraoxonase-1 and its relevance to enzyme activity and resistance to oxidative stress

Xenia Moren^*, Sara Deakin^*, Ming-Lin Liu, Marja-Riitta Taskinen and Richard W. James^1,*

^* Clinical Diabetes Unit, Department of Internal Medicine, University Hospital, Geneva, Switzerland
Division of Endocrinology, Thomas Jefferson University, Philadelphia, PA
Department of Internal Medicine, Helsinki University Central Hospital, Helsinki, Finland

The study was supported by a grant from the Swiss National Research Foundation (R.W.J.), an Erityisvaltionosuus grant from Helsinki University Central Hospital (M.R.T.), and by a Beginning Grant-In-Aid, Grant 0765254U (M-L.L.), from the American Heart Association.

Published, JLR Papers in Press, February 26, 2008.

¹ To whom correspondence should be addressed. e-mail: Richard.James{at}hcuge.ch

The subfraction distribution of HDL-associated peptides has implications for their functions and the impact of pathological modifications to lipoprotein metabolism on these functions. We have analyzed the subfraction distribution of paraoxonase-1 (PON1) and the consequences for enzyme activity and stability. HDL subfractions were defined by the presence (LpA-I,A-II) or absence (LpA-I) of apolipoprotein A-II (apoA-II). PON1 was present in both subfractions, although increased concentrations of HDL were associated with significantly increased PON1 in LpA-I. ApoA-II did not modify the capacity of native human HDL or reconstituted HDL to promote PON1 secretion from cells or to stabilize enzyme activity, nor did apoA-II decrease PON1 activity when added to rabbit serum normally devoid of the apolipoprotein. LpA-I,A-II particles isolated from human serum or reconstituted HDL (LpA-I,A-II) showed a significantly greater capacity than HDL(LpA-I) to stabilize secreted PON1 and purified recombinant PON1 added to such particles. PON1 associated with apoA-II-containing particles showed greater resistance to inactivation arising from oxidation. ApoA-I, apoA-II, and LpA-I,A-II, but not LpA-I, were independent determinants of serum PON1 concentration and activity in multivariate analyses. PON1 is at least equally distributed between LpA-I and LpA-II,A-II HDL particles. This dichotomous distribution has implications for PON1 activity and stability that may impact on the physiological role of the enzyme.

Supplementary key words lipoprotein • atherosclerosis • ApoA-I • ApoA-II

Abbreviations: AAPH, 2,2'-azobis (2-amidinopropane) hydrochloride; apoA-II, apolipoprotein A-II; ARE, arylesterase; CHO, Chinese hamster ovary; PON1, paraoxonase-1

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