Multiple Substrates for Paraoxonase-1 during Oxidation of Phosphatidylcholine by Peroxynitrite

Ahmed, Zakaria; Ravandi, Amir; Maguire, Graham F.; Emili, Andrew; Draganov, Dragomir; Du, Bert N. La; Kuksis, A.; Connelly, Philip W.

doi:10.1006/bbrc.2001.6150

Cited by 88 publications

(51 citation statements)

References 40 publications

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“…It is now clear that minor contaminants are present in these preparations, which has resulted in erroneous conclusions about some of the properties of purified PON1. For example, purified PON1 was reported to have PLA 2 activity (13,19). However, more recent evidence suggests that the reported activities are attributable to a small amount of PLA 2 contaminating the PON preparations (20, 21; our unpublished observations).…”

mentioning

confidence: 80%

Purified human serum PON1 does not protect LDL against oxidation in the in vitro assays initiated with copper or AAPH

Teiber

Draganov

2004

Journal of Lipid Research

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Purified serum paraoxonase (PON1) had been shown to attenuate the oxidation of LDL in vitro. We critically reevaluated the antioxidant properties of serum PON1 in the in vitro assays initiated with copper or the free radical generator 2,2 -azobis-2-amidinopropane hydrochloride (AAPH). The antioxidant activity of different purified PON1 preparations did not correlate with their arylesterase (AE), lactonase, or phospholipase A 2 activities or with the amounts of detergent or protein. Dialysis of three of these preparations resulted in a 30-40% loss of their AE activities but in a complete loss of their antioxidant activities. We also followed the distribution of the antioxidant activity during human serum PON1 purification by two purification methods. The antioxidant activity of the anion-exchange chromatography fractions did not copurify with PON1 using either method and could largely be accounted for by the "antioxidant" activity of the detergent present.In conclusion, using the copper or AAPH in vitro assays, no PON1-mediated antioxidant activity was detected, suggesting that the removal of PON1 from its natural environment may impair its antioxidative activity and that this assay with highly purified PON1 may be an inappropriate method with which to study the antioxidative properties of the enzyme.

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confidence: 80%

Purified human serum PON1 does not protect LDL against oxidation in the in vitro assays initiated with copper or AAPH

Teiber

Draganov

2004

Journal of Lipid Research

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“…Highly purified serum PON1 was reported to possess phospholipase A 2 (PLA 2 ) activity (38,39). We used thio-PAF as a surrogate substrate to test the recombinant PONs for PLA 2 activity.…”

Section: Enzymatic Activities Of the Purified Recombinant Human Ponsmentioning

confidence: 99%

Human paraoxonases (PON1, PON2, and PON3) are lactonases with overlapping and distinct substrate specificities

Draganov

Teiber

Speelman

et al. 2005

Journal of Lipid Research

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639

591

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The paraoxonase (PON) gene family in humans has three members, PON1 , PON2 , and PON3 . Their physiological role(s) and natural substrates are uncertain. We developed a baculovirus-mediated expression system, suitable for all three human PONs, and optimized procedures for their purification. The recombinant PONs are glycosylated with high-mannose-type sugars, which are important for protein stability but are not essential for their enzymatic activities. Enzymatic characterization of the purified PONs has revealed them to be lactonases/lactonizing enzymes, with some overlapping substrates (e.g., aromatic lactones), but also to have distinctive substrate specificities. All three PONs metabolized very efficiently 5-hydroxy-eicosatetraenoic acid 1,5-lactone and 4-hydroxy-docosahexaenoic acid, which are products of both enzymatic and nonenzymatic oxidation of arachidonic acid and docosahexaenoic acid, respectively, and may represent the PONs' endogenous substrates. Organophosphates are hydrolyzed almost exclusively by PON1, whereas bulky drug substrates such as lovastatin and spironolactone are hydrolyzed only by PON3. Of special interest is the ability of the human PONs, especially PON2, to hydrolyze and thereby inactivate N -acyl-homoserine lactones, which are quorum-sensing signals of pathogenic bacteria.

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“…Thus, LCAT either does not contribute to F 2 -IP release, it does so to a much lower extent than PAF acetylhydrolase, or it requires additional components for optimal activity. PON-1 has been reported previously to utilize PAF (24), oxidized phospholipids (25), and esterified IPs (25) as substrates. However, Marathe et al (26) demonstrated that minute contamination of PON-1 preparations with PAF acetylhydrolase account for the phospholipase activity previously ascribed to PON-1, a finding later confirmed by Connelly et al (27).…”

Section: An Enzymatic Activity In Human Plasma Releases Free F 2 -Ipsmentioning

confidence: 99%

Release of Free F2-isoprostanes from Esterified Phospholipids Is Catalyzed by Intracellular and Plasma Platelet-activating Factor Acetylhydrolases

Stafforini

Sheller

Blackwell

et al. 2006

Journal of Biological Chemistry

199

135

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F 2 -isoprostanes are produced in vivo by nonenzymatic peroxidation of arachidonic acid esterified in phospholipids. Increased urinary and plasma F 2 -isoprostane levels are associated with a number of human diseases. These metabolites are regarded as excellent markers of oxidant stress in vivo. Isoprostanes are initially generated in situ, i.e. when the arachidonate precursor is esterified in phospholipids, and they are subsequently released in free form. Although the mechanism(s) responsible for the release of free isoprostanes after in situ generation in membrane phospholipids is, for the most part, unknown, this process is likely mediated by phospholipase A 2 activity(ies). Here we reported that human plasma contains an enzymatic activity that catalyzes this reaction. The activity associates with high density and low density lipoprotein and comigrates with platelet-activating factor (PAF) acetylhydrolase on KBr density gradients. Plasma samples from subjects deficient in PAF acetylhydrolase do not release F 2 -isoprostanes from esterified precursors. The intracellular PAF acetylhydrolase II, which shares homology to the plasma enzyme, also catalyzes this reaction. We found that both the intracellular and plasma PAF acetylhydrolases have high affinity for esterified F 2 -isoprostanes. However, the rate of esterified F 2 -isoprostane hydrolysis is much slower compared with the rate of hydrolysis of other substrates utilized by these enzymes. Studies using PAF acetylhydrolase transgenic mice indicated that these animals have a higher capacity to release F 2 -isoprostanes compared with nontransgenic littermates. Our results suggested that PAF acetylhydrolases play key roles in the hydrolysis of F 2 -isoprostanes esterified on phospholipids in vivo.2 are a family of prostaglandin (PG)-like compounds produced in vivo primarily by a nonenzymatic, free radicalinduced oxidation of arachidonic acid (1). These compounds are generated in situ esterified to phospholipids through the formation of PGH 2 -like bicyclic endoperoxide intermediates. These intermediates can either undergo rearrangement to E 2 /D 2 -IPs, isothromboxanes, and highly reactive isoketals or become reduced to F 2 -IPs that have been characterized in detail. Following in situ oxidation, IPs are released in free form by the action of phospholipase(s) activity.The measurement of F 2 -IPs in biological fluids has become one of the most accepted quantitative assessments of lipid peroxidation and oxidant stress reactions that occur in vivo (2). This approach provides the advantage of being noninvasive, as F 2 -IPs circulate freely in plasma and are excreted in urine. Increased IP production has been observed in a number of human diseases associated with oxidant stress, including atherosclerosis, pulmonary and liver diseases, habitual smoking, neurological disorders, and diabetes (3-5). In addition, exposure of experimental animals to increased oxidant stress also results in remarkable increases in the levels of free IPs in the urine and in plasma (2, 6). P...

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Multiple Substrates for Paraoxonase-1 during Oxidation of Phosphatidylcholine by Peroxynitrite

Cited by 88 publications

References 40 publications

Purified human serum PON1 does not protect LDL against oxidation in the in vitro assays initiated with copper or AAPH

Purified human serum PON1 does not protect LDL against oxidation in the in vitro assays initiated with copper or AAPH

Human paraoxonases (PON1, PON2, and PON3) are lactonases with overlapping and distinct substrate specificities

Release of Free F2-isoprostanes from Esterified Phospholipids Is Catalyzed by Intracellular and Plasma Platelet-activating Factor Acetylhydrolases

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