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Analyte: Paraoxonase-1 Activity
Specimen Type: Serum, Inquire for additional option(s)
Optimum Volume: 0.5 mL
|5 days||2 months||1 yeary|
Reporting units: U*/L
Biological or Clinical Significance:
Paraoxonase is a single glycoprotein that is able to hydrolyze aromatic carboxylic acid esters as well as organophosphate compounds. Because of these alternative substrates, this enzyme has been called arylester hydrolase or paraoxonase. It is closely associated with HDL lipoprotein particles and has a molecular mass of 43 kD. Paraoxonase activity is apparently associated only with a small fraction of the HDL particles.
The enzyme is found as two different alleles, one containing arginine at position 192 (PON1 B), while the other contains glutamine (PON1 A). The later has decreased activity against paraoxon and other organophosphate compounds. Minimally oxidized-LDL contains multioxygenated phospholipids, including 1-palmitoyl 2-arachidonyl phophatidylcholine, which is a substrate for paraoxonase. Individuals with diabetes mellitus or familial hypercholesterolemia have reduced paraoxonase activity, and perhaps are more likely to carry the PON1 A gene. This may facilitate the development of atherosclerosis because of the failure to inhibit the continued oxidative modification of LDL. Studies in the last two decades have demonstrated Paraoxonase's ability to protect against atherosclerosis by hydrolyzing specific derivatives of oxidized cholesterol and/or phospholipids in oxidized low-density lipoprotein and in atherosclerotic lesions.
Principle of Test Method:
Paraoxonase activity can be measured by a modification of the methods of Krisch and Eckerson as described by Haagen and Brock (see references). This assay, is adapted to an auto-analyzer which measures the initial velocity of the substrate formation to determine the activity of the enzyme. *U: mmol/minute (Amount of enzyme that would convert 1 mmol of substrate per minute under standard conditions),
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2. Mackness MI, Arrol S,Abbott C, Druuington PN. Protection of low-density lipoprotein against oxidative modification by high-density lipoprotein associated prraoxonase. Atherosclerosis 1993; 104:129-35.
3. Krisch K: Enzymatische Hydrolyse von Diathyl-p-nitrophenylphosphat (E600) durch menchliches Serum. Z Klin Chem Llin Biochem 1:41-45, 1968.
4. Eckerson, HW, Wyte, CM and La Du, BN: The human serum paraoxonase / arylesterase polymorphism. Am. J. Hum. Genet. 35, 1126-38, 1983.
5. Haagen L and Brock A. A new automated method for phenotyping arylesterase (EC 22.214.171.124) based upon inhibition of enzymatic hydrolysis of 4-nitrophenyl acetate by phenyl acetate. Eur J Clin ChemClin Biochem. 1992; 30 (7), 391-5.
6. Sklan EH, Lowenthal A, Korner M, Ritov Y, Landers DM, Rankinen T, et. al. Acetylcholinesterase / paraoxonase genotype and expression predict anxiety scores in health, risk factors, exercise training and genetics study. PNAS. 101, 5512-5517, 2004.
7. Draganov DI, La Du BN. Pharmacogenetics of paraoxonases: a brief review. Naunyn-Schmiedeberg’s archives of pharmacology 2004; 369: 78-88.