Organofosfatlı pestisit zehirlenmeleri ve serum paraoksonaz 1 PON1 enziminin organofosfat metabolizmasındaki rolü

Year 2010, Volume: 67 Issue: 2, 97 - 112, 01.06.2010

Birsen Can Demirdöğen

Abstract

Dünya Sağlık Örgütü’nün verilerine göre tüm dünyada yılda 3 milyona yakın pestisit zehirlenmesi meydana gelmekte, bunların 220.000’i ölümle sonuçlanmaktadır. Son yıllarda sıklıkla kullanılan pestisitlerden olan organofosfatlar, sinir sistemi üzerinde etki gösteren kimyasallardır. Organofosfatlar asetilkolinesteraz enzimini baskılayarak nörotoksisiteye yol açarlar. Paraoksonaz 1 PON 1; EC 3.1.8.1 serumda yüksek dansiteli lipoprotein HDL üzerinde yer alan, kalsiyuma bağımlı glikoprotein yapısında bir enzimdir. Memelilerin birçok organında PON1 aktivitesi tespit edilmesine karşın, kuşlar, balıklar ve böceklerde paraoksonaz aktivitesi sıfıra yakındır. PON1’in hidrolize ettiği substratlar arasında paration, diazinon ve klorprifos gibi organofosfatlı insektisitlerin aktif formu olan toksik okson metabolitleri; sarin, ve soman gibi sinir gazları; fenil asetat gibi aromatik esterler; homogentisik asit lakton, dihidrokumarin ve homosistein tiolakton gibi birçok aromatik ve alifatik lakton ile siklik karbonatlar yer almaktadır. Organofosfatlı pestisitlerin toksikolojisi ile ilgili yapılan ilk çalışmalar düşük serum PON1 aktivitesine sahip olmanın organofosfatlı bileşiklerin akut etkilerine karşı duyarlılığı arttırdığını ortaya koymuştur. PON1’i kodlayan genin sekansının belirlenmesinin ardından, kişiler arasında enzimin aktivitesinde ve ifade edilme seviyesinde farklılıklara yol açan polimorfizmler tespit edilmesi, PON1 aktiviteleri düşük olan insanların organofosfat zehirlenmelerine karşı daha hassas olabileceğini düşündürmüştür. Son yıllarda yapılan çalışmalarda saflaştırılmış PON1’in organofosfatlı pestisitlere maruz kalan hayvanlara enjekte edilmesi, dolayısı ile serum PON1 seviyesinin yapay olarak arttırılması ile klorprifos ve diazinon gibi bazı organofosfatların toksik etkilerini azaltmanın mümkün olduğu gösterilmiş, ancak bu uygulamanın paration maruziyetine karşı etkili olmadığı görülmüştür. Her ne kadar paraoksonu hidrolizleyen enzim olarak tanınsa da, PON1’in paraoksonaz aktivitesi nispeten zayıftır. Organofosfat maruziyetine karşı koruyucu olarak kullanılabilmesi için PON1’in katalitik verimi arttırılmalı ve yeterli miktarda elde edilebilmelidir. Son yıllarda protein mühendisliği yöntemleri kullanılarak PON1’in bazı amino asitlerinde değişiklikler yapılmış, bu PON1 varyantları bakteriyel sistemlerde yeterli seviyelerde ifade edilmiş ve bazı organofosfatlara karşı enzim aktivitesinde artışlar sağlanmıştır. Bu derlemede, öncelikle organofosfatların genel özelliklerine, etki mekanizmalarına ve zehirlenmelere değinilmiş, ardından PON1’in organofosfat metabolizmasındaki rolüne ve organofosfat zehirlenmelerinde antidot olarak kullanılabilmesine yönelik araştırmalardaki son gelişmeler üzerinde durulmuştur.

Keywords

Antidot, insektisit, organofosfat, paraoksonaz, pestisit, PON1

Organophosphate pesticide poisonings and the role of serum paraoxonase 1 PON1 enzyme in organophosphate metabolism

Abstract

According to data from the World Health Organization, nearly 3 million pesticide poisonings occur per year worldwide; 220,000 of these poisonings result in death. Organophosphates, one of the most frequently used pesticides in recent years, are chemicals that effect the nervous system. Organophosphates lead to neurotoxicity by suppressing the enzyme acetylcholinesterase. Paraoxonase 1 PON 1; EC 3.1.8.1 is a calcium dependent glycoprotein enzyme that is found on the high density lipoprotein HDL in serum. Although PON1 activity has been detected in several organs of mammals, paraoxonase activity is close to zero in birds, fish and insects. Among the chemicals that are hydrolized by PON1; the toxic oxon metabolites of organophosphate inseciticides, which are the active forms, such as parathion, diazinon and chlorpyrifos; nerve gases such as sarin and soman; aromatic esters such as phenyl acetate; several aromatic and aliphatic lactones such as homogentisic acid lactone, dihydrocoumarin and homocysteine thiolactone and cyclic carbonates are included. Earlier studies on the toxicology of organophosphate pesticides revealed that having low serum PON1 activity increases the senstivity to the acute effects of organophosphate compounds. Following determination of the sequence of the gene encoding PON1, identification of polymorphisms that lead to differences among people in the activity and level of expression of the enzyme, led to the idea that people with low PON1 activity may be more sensitive to organophosphate poisoning. In studies carried out in recent years, it was shown that injection of purified PON1 to animals that are exposed to organophosphate pesticides, and thus increasing serum PON1 levels artificially, it was possible to reduce the toxic effects of certain organophosphates like chlorpyrifos and diazinon; but this application was observed to be ineffective against parathion exposure. Even though recognized as the enzyme that hydrolyzes paraoxon, paraoxonase activity of PON1 is a bit weak. In studies carried out in recent years, it was observed that injection of purified PON1 protects against chlorpyrifos and diazinon but was not effective against parathion exposure. In order to be used as a prophylactic agent against organophosphate exposure, PON1’s catalytic efficiency has to be increased and the enzyme has to be obtained in adequate amounts. In recent years, using protein engineering methods, changes were made to some amino acids of PON1, these PON1 variants were expressed in bacterial systems at sufficient levels and increase in enzyme activity against some organophosphates were obtained. In this review, first, general aspects of organophosphates, action mechanism and poisonings are addressed; then, the role of PON1 in organophosphate metabolism and recent advances in the research intended for improving PON1 so that it can be used as an antidote in organophosphate poisonings are empasized

Keywords

Antidote, insecticide, organophosphate, paraoxonase, pesticide, PON1, poisoning

References

• World Health Organization. Informal consultation on planning strategy for the prevention of pesticide poisoning, WHO, Geneva, WHO/VBC/86.926, 1986.
• World Health Organization. Public health impact of pesticides used in agriculture, WHO, Geneva, 1990.
• Ulusal Zehir Danışma Merkezi 2008 yılı çalışma raporu özeti. Türk Hij Den Biyol Derg, 2009; 66 (3) Ek 3.
• World Health Organization. Public health impact of pesticides used in agriculture, Report of WHO/UNEP working group, WHO, Geneva, 1989.
• Güler Ç, Çobanoğlu Z. Pestisitler. Çevre Sağlığı Temel Kaynak Dizisi. 1. Basım. T.C. Sağlık Bakanlığı Yayınları, Ankara, 1997: 37-8.
• Jeyaratnam J, De Alwis Seneviratne RS, Copplestone JF. Survey of pesticide poisoning in Sri Lanka. Bull World Health Organ, 1982; 60(4): 615-19.
• Jeyaratnam J. Health problems of pesticide usage in the Third World. Br J Ind Med, 1985; 42: 505-6. http://emedicine.medscape.com/article/167726- overview erişim tarihi: 10.12.2009
• Costa LG. Current issues in organophosphate toxicology. Clin Chim Acta, 2006; 366(1-2): 1-13.
• Sataloğlu N, Aydın B, Turla A. Pestisit Zehirlenmeleri. Kor Hek, 2007; 6 (3): 169-74.
• van der Hoek W, Konradsen F. Risk factors for acute pesticide poisoning in Sri Lanka. Trop Med Int Health, 2005; 10 (6) : 589-96.
• Nagami H, Nishigaki Y, Matsushima S, Matsushita T, Asanuma S, Yajima N, Usuda M, Hirosawa M. Hospital-based survey of pesticide poisoning in Japan, 1998-2002. Int J Occup Environ Health, 2005; 11(2): 180-4
• Abdollahi M, Jalali N, Sabzevari O, Hoseini R, Ghanea T. A retrospective study of poisoning in Tehran. J Toxicol Clin Toxicol, 1997; 35(4): 387-93.
• Eyer P, Szinicz L, Thiermann H, Worek F, Zilker T. Testing of antidotes for organophosphorus compounds: Experimental procedures and clinical reality. Toxicology, 2007; 233 (1-3): 108–19.
• Suzuki T, Morito H, Ono K, Mackawa K, Nagai R, Yazaki Y. Sarin poisoning in Tokyo subway. Lancet, 1995; 345: 980-1.
• Katz KD, Brooks DE. Toxicity, Organophosphate. http:// emedicine.medscape.com/article/167726-overview Son erişim tarihi: 15.10.2009. http://npic.orst.edu/RMPP/rmpp_ch4.pdf erişim tarihi: 11.12.2009
• La Du BN. Human serum paraoxonase/arylesterase. In: Kalow W, Ed. Pharmacogenetics of Drug Metabolism. New York: Pergamon Press, 1992.
• Costa LG, Cole TB, Jarvik GP, Furlong CE. Functional genomics of the paraoxonase (PON1) polymorphisms: Effects on pesticide sensitivity, cardiovascular disease, and drug metabolism. Annu Rev Med, 2003; 54: 371–92.
• Luft FC. Insecticides and atherosclerosis. J Mol Med, 2001; 79: 415-6.
• Rusyniak DE, Nañagas KA. Organophosphate poisoning. Semin Neurol, 2004; 24: 197–204.
• Adanır T, Çetin Uysal F, Aksun M, Kurt Y, Özvardar Y, Savacı S. Paratiyon ve malatiyon ile gelişen iki organik fosfor entoksikasyonu. Türk Anest Rean Der Dergisi, 2005; 33: 186-91.
• Broomfield CA, Maxwell DM, Solana RP, Castro CA, Finger AV, Lenz DE. Protection by butyrylcholinesterase against organophosphorus poisoning in nonhuman primates. J Pharmacol Exp Ther, 1991; 259(2): 633-8.
• Saxena A, Sun W, Luo C, Myers TM, Koplovitz I, Lenz DE, Doctor BP. Bioscavenger for protection from toxicity of organophosphorus compounds. J Mol Neurosci, 2006; 30 (1-2):145-8.
• Lenz DE, Yeung D, Smith JR, Sweeney RE, Lumley LA, Cerasoli DM. Stoichiometric and catalytic scavengers as protection against nerve agent toxicity: A mini review. Toxicology, 2007; 233 (1-3): 31-9.
• Stevens RC, Suzuki SM, Cole TB, Park SS, Richter RJ, Furlong CE. Engineered recombinant human paraoxonase 1 (rHuPON1) purified from Escherichia coli protects against organophosphate poisoning. Proc Natl Acad Sci USA, 2008; 105(35): 12780-4.
• Gan KN, Smolen A, Eckerson H, La Du BN. Purification of human serum paraoxonase/arylesterase: evidence for one esterase catalyzing both activities. Drug Metab Dispos, 1991; 19: 100-6.
• Hassett C, Richter RJ, Humbert R, Chapline C, Crabb JW, Omiecinski CJ, Furlong CE. Characterization of cDNA clones encoding rabbit and human serum paraoxonase: the mature protein retains its signal sequence. Biochemistry, 1991; 30: 10141-9.
• Sorenson RC, Bisgaier CL, Aviram M, Hsu C, Billecke S, La Du BN. Human serum paraoxonase/arylesterase’s retained hydrophobic N-terminal leader sequence associates with HDLs by binding phospholipids: apolipoprotein A-I stabilizes activity. Arterioscler Thromb Vasc Biol, 1999; 19: 2214-25.
• Blatter M-C, James RW, Messmer S, Barja F, Pometta D. Identification of a distinct human high-density lipoprotein subspecies defined by a lipoproteinassociated protein, K-85: identity of K-85 with paraoxonase. Eur J Biochem, 1993; 211: 871-9.
• Draganov DI, La Du BN. Pharmacogenetics of paraoxonases: a brief review. Naunyn Schmiedebergs Arch Pharmacol, 2004; 369(1): 78-88.
• Humbert R, Adler DA, Disteche CM, Hassett C, Omiecinski CJ, Furlong CE. The molecular basis of the human serum paraoxonase activity polymorphism. Nat Genet, 1993; 3: 73-6.
• Tougou K, Nakamura A, Watanabe S, Okuyama Y, Morino A. Paraoxonase has a major role in the hydrolysis of prulifloxacin (NM441), a prodrug of a new antibacterial agent. Drug Metab Dispos, 1998; 26(4): 355-9.
• Chambers JE. PON1 multitasks to protect health. PNAS, 2008; 105 (35): 12639-40.
• Mackness MI, Arrol S, Abbott CA, Durrington PN. Protection of low-density lipoprotein against oxidative modification by high-density lipoprotein associated paraoxonase. Atherosclerosis, 1993; 104: 129-35.
• Steinberg D, Parthasarathy S, Carew TE, Khoo JC, Witztum JL. Beyond cholesterol: modifications of low density lipoprotein that increase its atherogenicity. N Engl J Med, 1989; 320: 915-24.
• Shih D, Gu L, Xia YR, et al. Mice lacking serum paraoxonase are susceptible to organophosphate toxicity and atherosclerosis. Nature, 1998; 394: 284-7.
• Mackness B, Quarck R, Verreth W, Mackness M, Holvoet P. Human paraoxonase-1 overexpression inhibits atherosclerosis in a mouse model of metabolic syndrome. Arterioscler Thromb Vasc Biol, 2006; 26: 1545-50.
• Serrato M, Marian AJ. A variant of human paraoxonase/ arylesterase (HUMPONA) gene is a risk factor for coronary artery disease. J Clin Invest, 1995; 96: 3005-8.
• Mackness B, Durrington P, McElduff P, et al. Low paraoxonase activity predicts coronary events in the Caerphilly prospective study. Circulation, 2003; 107(22): 2775-9.
• Can Demirdöğen B, Türkanoğlu A, Bek S, et al. Paraoxonase/arylesterase ratio, PON1 192Q/R polymorphism and PON1 status are associated with increased risk of ischemic stroke. Clin Biochem, 2008; 41 (1-2): 1-9.
• Demirdöğen BC, Demirkaya Ş, Türkanoğlu A, Bek S, Arınç S, Adalı O. Analysis of paraoxonase 1 (PON1) genetic polymorphisms and activities as risk factors for ischemic stroke in Turkish population. Cell Biochem Funct, 2009; 27(8): 558-67.
• Brealey CB, Walker CH, Baldwin BC. A-esterase activities in relation to the differential toxicity of pirimiphosmethyl to birds and mammals. Pestic Sci, 1980; 11: 546-54.
• Mackness B, Durrington PN, Mackness MI. Human serum paraoxonase. Gen Pharmacol, 1998; 31: 329-36.
• Main AR. The role of A-esterase in the acute toxicity of paraoxon, TEPP and parathion. Can J Biochem Physiol, 1956; 34: 197-216.
• Costa LG, McDonald BE, Murphy SD, et al. Serum paraoxonase and its influence on paraoxon and chlorpyrifos-oxon toxicity in rats. Toxicol Appl Pharmacol, 1990; 103: 66-76.
• Li W-F, Costa LG, Furlong CE. Serum paraoxonase status: A major factor in determining resistance to organophosphates. J Toxicol Environ Health, 1993; 40: 337-46.
• Li W-F, Furlong C, Costa LG. Paraoxonase protects against chlorpyrifos toxicity in mice. Toxicol Lett, 1995; 76: 219-26.
• Cowan J, Sinton CM, Varley AW, Wians FH, Haley RW, Munford RS. Gene therapy to prevent organophosphate intoxication. Toxicol Appl Pharmacol, 2001; 173: 1-6.
• Li WF, Costa LG, Richter RJ, et al. Catalytic efficiency determines the in vivo efficacy of PON1 for detoxifying organophosphates. Pharmacogenetics, 2000; 10: 767-79.
• Chambers JE, MaT, Boone JS, Chambers HW. Role of detoxication pathways in acute toxicity levels of phosphorothionate insecticides in the rat. Life Sci, 1994; 54: 1357-64.
• Costa LG, Cole TB, Furlong CE. Polymorphisms of paraoxonase (PON1) and their significance in clinical toxicology of organophosphates. J Toxicol Clin Toxicol, 2003; 41(1): 37-45.
• Augustinsson KB, Barr M. Age variation in plasma arylesterase activity in children. Clin Chim Acta, 1963; 8: 568-73.
• Weitman SD, Vodicnick MJ, Lech TJ. Influence of pregnancy on parathion toxicity and disposition. Toxicol Appl Pharmacol, 1983; 71: 215-24.
• McElveen J, Mackness MI, Colley CM, Peard T, Warner S, Walker CH. Distribution of paraoxon hydrolytic activity in the serum of patients after myocardial infarction. Clin Chem, 1986; 32: 671-3.
• Ayub A, Mackness MI, Arrol S, Mackness B, Patel J, Durrington PN. Serum paraoxonase after myocardial infarction. Arterioscler Thromb Vasc Biol, 1999; 19: 330-5.
• Jarvik GP, Rozek LS, Brophy VH, et al. Paraoxonase (PON1) phenotype is a better predictor of vascular disease than is PON1(192) or PON1(55) genotype. Arterioscler Thromb Vasc Biol, 2000; 20: 2441-7.
• Patel BN, Mackness MI, Harty DW, Arrol S, BootHandford RP, Durrington PN. Serum esterase activities and hyperlipidemia in the streptozotocin-diabetic rat. Biochem Biophys Acta, 1990; 1035: 113-6.
• Mackness MI, Harty D, Bhatnagar D, et al. Serum paraoxonase activity in familial hypercholesterolaemia and insulin - dependent diabetes mellitus. Atherosclerosis, 1991; 86: 193-9.
• Hasselwander O, McMaster D, Fogarty DG, Maxwell AP, Nicholls DP, Young IS. Serum paraoxonase and plateletactivating factor acetylhydrolase in chronic renal failure. Clin Chem, 1998; 44: 179-81.
• Tanimoto N, Kumon Y, Suehiro T, et al. Serum paraoxonase activity decreases in rheumatoid arthritis. Life Sci, 2003; 72: 2877-85.
• Ferré N, Camps J, Cabré M, Paul A, Joven J. Hepatic paraoxonase activity alterations and free radical production in rats with experimental cirrhosis. Metabolism, 2001; 50: 997-1000.
• Paragh G, Balla P, Katona E, Seres I, Egerhazi A, Degrell I. Serum paraoxonase activity changes in patients with Alzheimer’s disease and vascular dementia. Eur Arch Psychiatry Clin Neurosci, 2002; 252: 63-7.
• Raiszadeh F, Solati M, Etemadi A, Azizi F. Serum paraoxonase activity before and after treatment of thryotoxicosis. Clin Endocrinol, 2004; 60: 75-80.
• Cakmak A, Zeyrek D, Atas A, Selek S, Erel O. Oxidative status and paraoxonase activity in children with asthma. Clin Invest Med, 2009; 32(5): E327-34.
• Shih DM, Gu L, Hama S, et al. Genetic-dietary regulation of serum paraoxonase expression and its role in atherogenesis in a mouse model. J Clin Invest, 1996; 97: 1630-9.
• Sutherland WHF, Walker RJ, de Jong SA, van Rij AM, Phillips V, Walker HL. Reduced postprandial serum paraoxonase activity after a meal rich in used cooking fat. Arterioscler Thromb Vasc Biol, 1999; 19: 1340-7.
• Boemi M, Sirolla C, Testa R, Cenerelli S, Fumelli P, James RW. Smoking is associated with reduced serum levels of the antioxidant enzyme, paraoxonase, in Type 2 diabetic patients. Diabet Med, 2004; 21, 423-7.
• Debord J, Dantoine T, Bollinger JC, Abraham MH, Verneuil B, Merle L. Inhibition of arylesterase by aliphatic alcohols. Chem Biol Interact, 1998; 113: 105-15.
• Beltowski J, Wojcicka G, Jamroz A. Effect of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) or tissue paraoxonase 1 and plasma platelet activating factor acetylhydrolase activities. J Cardiovasc Pharmacol, 2004; 43: 121-7.
• Pope CN, Liu J. Age-related difference in sensitivity to organophosphorus pesticides. Environ Toxicol Pharmacol, 1997; 4: 309-14.
• Ecobichon DJ, Stephens DS. Perinatal development of human blood esterases. Clin Pharmacol Ther, 1973; 14: 41-7.
• Milochevitch C, Khalil A. Study of the paraoxonase and plateletactivating factor acetylhydrolase activities with aging. Prostagl Leukot Essent Fatty Acids, 2001; 65: 241-6.
• Eckerson HW, White CM, La Du BN. The human serum paraoxonase/arylesterase polymorphism. Am J Hum Genet, 1983; 35: 1126-38.
• Davies HG, Richter RJ, Keifer M, Broomfield CA, Sowalla J, Furlong CE. The effect of the human serum paraoxonase polymorphism is reversed with diazoxon, soman and sarin. Nat Genet, 1996; 14: 334-6.
• Blatter Garin MC, James RW, Dussoix P, et al. Paraoxonase polymorphism Met-Leu 54 is associated with modified serum concentrations of the enzyme. A possible link between the paraoxonase gene and increased risk of cardiovascular disease in diabetes. J Clin Invest, 1997; 99: 62-6.
• Brophy VM, Hastings MD, Clendenning JB, Richter RJ, Jarvik GP, Furlong CE. Polymorphisms in the human paraoxonase (PON1) promoter. Pharmacogenetics, 2001; 11: 77-84.
• Brophy VH, Jampsa RL, Clendenning JB, McKinstry LA, Jarvik GP, Furlong CE. Effects of 5’ regulatory-region polymorphisms on paraoxonase gene (PON1) expression. Am J Hum Genet, 2001; 68: 1428-36.
• Cole TB, Walter BJ, Costa LG, et al. Contribution of paraoxonase (PON1) levels and Q192R genotype to organophosphate detoxication: evidence from humans and “humanized” transgenic mice. Toxicol Sci, 2003; 72 (Suppl. 1): 100.
• Costa LG, Cole TB, Vitalone A, Furlong CE. Measurement of paraoxonase (PON1) status as a potential biomarker of susceptibility to organophosphate toxicity. Clin Chim Acta, 2005; 352: 37-47.
• Brophy VH, Jarvik GP, Furlong CE. PON1 polymorphisms. In: Costa LG, Furlong CE, eds. Paraoxonase (PON1) in Health and Disease: Basic and Clinical Aspects. Norwell, MA: Kluwer Academic Publishers, 2002: 53-77.
• Yamasaki Y, Sakamoto K, Watada H, Kajimoto Y, Hori M. The Arg192 isoform of paraoxonase with low sarinhydrolyzing activity is dominant in the Japanese. Hum Genet, 1997; 101:67-8.
• Yamada Y, Takatori T, Nagao M, Iwase H, Kurada N, Yanagida J, Shinozuka T. Expression of paraoxonase isoform did not confer protection from acute sarin poisoning in the Tokyo subway terrorist attack. Int J Leg Med, 2001; 115: 82-4.
• Institute of Medicine, Gulf War and Health. Vol. 1. Depleted Uranium, Pyridostigmine Bromide, Sarin, Vaccines. Washington, DC: National Academy Press, 2000; p. 408.
• Haley RW, Billecke S, La Du BN. Association of low PON1 type Q (type A) arylesterase activity with neurologic symptom complexes in Gulf War veterans. Toxicol Appl Pharmacol, 1999; 157: 227-33.
• Mackness B, Durrington PN, Mackness MI. Low paraoxonase in Persian gulf War veterans self-reporting Gulf War Syndrome. Biochem Biophys Res Commun, 2000; 276: 729-33.
• Pilkington A, Buchanan D, Jamal GA, et al. An epidemiological study of the relations between exposure to organophosphate pesticides and indices of chronic peripheral neuropathy and neuropsychological abnormalities in sheep farmers and dippers. Occup Environ Med, 2001; 58: 702-10.
• Cherry N, Mackness MI, Durrington P, et al. Paraoxonase (PON1) polymorphisms in farmers attributing ill health to sheep dip. Lancet, 2002; 359: 763-4.
• Mackness B, Durrington P, Povey A, et al. Paraoxonase and susceptibility to organophosphorus poisoning in farmers dipping sheep. Pharmacogenetics, 2003; 13(2): 81-8.
• Sozmen EY, Mackness B, Sozmen B, et al. Effect of organophosphate intoxication on human serum paraoxonase. Hum Exp Toxicol, 2002; 21: 247-52.
• Harel M, Brumshtein B, Meged R, et al. The 3-D structure of serum paraoxonase 1 sheds light on its activity, stability, solubility, and crystallizability. Arh Hig Rada Toksikol, 2007; 58: 347-53.
• Yeung DT, Josse D, Nicholson JD, et al. Structure/ function analyses of human serum paraoxonase (HuPON1) mutants designed from a DFPase-like homology model. Biochim Biophys Acta, 2004; 1702: 67-77.
• Yeung DT, Lenz DE, Cerasoli DM. Analysis of active-site amino-acid residues of human serum paraoxonase using competitive substrates. FEBS J, 2005; 272: 2225- 30.
• Aharoni A, Gaidukov L, Yagur S, Toker L, Silman I, Tawfik DS. Directed evolution of mammalian paraoxonases PON1 and PON3 for bacterial expression and catalytic specialization. Proc Natl Acad Sci USA, 2004; 101(2): 482-7.
• Otto TC, Harsch CK, Yeung DT, Magliery TJ, Cerasoli DM, Lenz DE. Dramatic differences in organophosphorus hydrolase activity between human and chimeric recombinant mammalian paraoxonase-1 enzymes. Biochemistry, 2009; 48(43): 10416-22.