Some cardiovascular therapeutics inhibit paraoxonase 1 (PON1) from human serum

Modulatory Effect of Lifestyle-Related, Environmental and Genetic Factors on Paraoxonase-1 Activity: A Review

Paraoxonase-1 (PON1) is a calcium-dependent, HDL-bound serum hydrolase active toward a wide variety of substrates. PON1 displays three types of activities, among which lactonase, paraoxonase, arylesterase and phosphotriesterase can be distinguished. Not only is this enzyme a major organophosphate compound detoxifier, but it is also an important constituent of the cellular antioxidant system and has anti-inflammatory and antiatherogenic functions. The concentration and activity of PON1 is highly variable among individuals, and these differences can be both of genetic origin and be a subject of epigenetic regulation. Owing to the fact that, in recent decades, the exposure of humans to an increasing number of different xenobiotics has been continuously rising, the issues concerning the role and activity of PON1 shall be reconsidered with particular attention to growing pharmaceuticals intake, dietary habits and environmental awareness. In the following manuscript, the current state of knowledge concerning the influence of certain modifiable and unmodifiable factors, including smoking, alcohol intake, gender, age and genotype variation on PON1 activity, along with pathways through which these could interfere with the enzyme's protective functions, is presented and discussed. Since exposure to certain xenobiotics plays a key role in PON1 activity, the influence of organophosphates, heavy metals and several pharmaceutical agents is also specified.

Synthesis, in vitro inhibition effect of novel phthalocyanine complexes as carbonic anhydrase and paraoxonase enzyme inhibitors

The preparation and assessment of carbonic anhydrase and paraoxonase enzyme inhibition properties of 3-(2-(5-amino-4-(4-bromophenyl)-3-methyl-1H-pyrazol-1-yl)ethoxy)phthalonitrile (2) and its nitrogen-containing non-peripheral phthalocyanine derivatives (3 and 4) are reported for the first time. The new phthalonitrile and its phthalocyanine derivatives have been elucidated by FT-IR spectroscopy, 1H-NMR, [Formula: see text]C-NMR, mass and UV-vis spectroscopy. The results demonstrated that all synthesized compounds moderately inhibited carbonic anhydrase and paraoxonase enzymes. Among the compounds, the most active ones were found to be compound 4 for PON (Ki : 0.14 [Formula: see text]M), compound 3 for hCA I (Ki : 22.52 [Formula: see text]M) and compound 1 for hCA II (Ki : 13.62 [Formula: see text]M).

PON-1 haplotype (-108C>T, L55M, and Q192R) modulates the serum levels and activity PONase promoting an atherogenic lipid profile in rheumatoid arthritis patients

INTRODUCTION/OBJECTIVE

Paraoxonase 1 (PON1) promotes antioxidant and antiatherogenic activity related to the hydrolysis of oxidized lipids of low-density lipoproteins. In rheumatoid arthritis (RA) patients, it has been reported that low PON1 activity is related to an impaired lipid profile, increasing cardiovascular risk (CVR). The goal of this study was to analyze the effect of common PON1 polymorphisms and haplotypes on enzymatic activity, PON1 serum levels (PON1s), and lipid parameters related to atherogenic profile in RA patients.

METHODS

A cross-sectional study was carried out on 250 Mexican patients with RA. The lipid profile was determined by colorimetric tests. The PON1 activity (CMPAase) was measured by spectrophotometry. The levels of PON1s were determined by ELISA, and the polymorphisms in the PON-1 gene (-108C>T, L55M, and Q192R) were genotyped by the PCR-RFLP method. The haplotypes were estimated and statistical analysis was performed.

RESULTS

The median of the CMPAase activity and PON1 levels was 13.91 U/mL and 24.75 ng/mL, respectively. The CMPAase activity was significantly lower in carriers of -108TT and 192QQ genotypes (β = - 4.09, P = 0.001 and β = - 3.73, P = 0.002, respectively); moreover, the PON1 levels were lower in 192Q allele carriers (P < 0.01). The TLQ haplotype was associated with CMPAase activity < 13.91 U/mL (OR = 2.29, P < 0.001), as well as with levels of PON1s < 24.75 ng/mL (OR = 1.65, P = 0.017). In this study, the CMPAase activity (< 13.91 U/mL) showed a positive association with lower levels of high-density lipoprotein cholesterol (HDL-c; < 40/50 mg/dL), and with a triglycerides/HDL-c ratio > 3%, and a total cholesterol/HDL-c ratio > 4.5/5%, all representatives of an atherogenic risk lipid profile.

CONCLUSIONS

PON1 polymorphisms modulate the CMPAase activity and PON1 levels in Mexican patients with RA. The CMPAase activity < 13.91 U/mL is associated with an atherogenic lipid profile, independently of inflammation markers and treatment with anti-rheumatic drugs. Key Points •The haplotype TLQ is a marker for low PONase activity in rheumatoid arthritis. •The haplotype TLQ is a marker for low PON1 serum levels in rheumatoid arthritis. •The enzymatic PON1 activity represents the best marker for an atherogenic lipid profile in rheumatoid arthritis, in comparison with PON1 levels. •The haplotype TLQ is a marker of low PON1 activity, levels of PON1s, and atherogenic lipid profile, independent of treatment therapy in rheumatoid arthritis.

Paraoxonase-1: Characteristics and Role in Atherosclerosis and Carotid Artery Disease

Paraoxonase-1 (PON-1) is a calcium-dependent enzyme that is synthesized in the liver and then secreted in blood where it is bound to high density lipoprotein (HDL). PON-1 is a hydrolase with a wide range of substrates, including lipid peroxides. It is considered responsible for many of the antiatherogenic properties of HDL. PON-1 prevents low density lipoprotein (LDL) oxidation, a process that is considered to contribute to the initiation and development of atherosclerosis. PON-1 activity and levels are influenced by gene polymorphisms; of the 2 common variants, one is in position 192 (Q192R) and one in position 55 (M55L). Also, many drugs affect PON-1 activity. The role of PON-1 in carotid atherosclerosis is inconsistent. Some studies show an association of PON-1 polymorphisms with carotid plaque formation, whereas others do not. The aim of this review is to summarize the characteristics of PON-1, its interactions with drugs and its role in atherosclerosis and especially its relationship with carotid artery disease.

Benzenesulfonamide derivatives containing imine and amine groups: Inhibition on human paraoxonase and molecular docking studies

Sulfonamides known as inhibitors of many metabolic enzymes have been widely used as antimicrobial drugs for a long time. In the present study, we investigated in vitro inhibitory activities of benzenesulfonamide derivatives on human paraoxonase-I (hPON1). For this aim, PON1 was purified from human serum with a specific activity of 2603.57 EU/mg and 8.34% yield using simple chromatographic methods. The various concentrations of early-synthesized sixteen sulfonamide derivatives were tested on the paraoxonase activity. Ki values of compounds were found in the range of 0.28-357.70 µM. Compound H4 had the highest inhibitory activity on hPON1 as competitive. Estimated structure-activity relationship (SAR) for compounds was done based on different substituents and their positions in the compounds. Besides, the molecular docking analysis of compound H4 was performed to understand the binding interactions on the active site of the enzyme. According to these experimental results, compound H4 was a potential inhibitor of PON1.

Some indazoles reduced the activity of human serum paraoxonase 1, an antioxidant enzyme: in vitro inhibition and molecular modeling studies

Background: Paraoxonase 1 (PON1: EC 3.1.8.1) is a vital antioxidant enzyme against mainly atherosclerosis and many other diseases associated with oxidative stress. Thus, studies related to PON1 have an important place in the pharmacology. In this study, we aimed to evaluate the in vitro inhibition effects of some indazoles on the activity of human PON1. Methods: PON1 was purified from human serum with a specific activity of 5000 U/mg and 13.50% yield by using simple chromatographic methods. Results: The indazoles showed K_i values in a range of 26.0 ± 3.00-111 ± 31.0 μM against hPON1. All these indazoles exhibited competitive inhibition. In addition, molecular docking studies were performed in order to assess the probable binding mechanisms into the active site of hPON1. Molecular modeling studies confirmed our results. Conclusions: Inhibition of PON1 by indazoles supplies a verification to further consideration of limitation dosage of indazole molecule groups as drug.

Differential effects of selective serotonin reuptake inhibitors on paraoxonase-1 enzyme activity: An in vitro study

Paraoxonase-I (PON1) is a calcium-dependent hydrolytic enzyme, plays an important role in most antioxidant properties related to high-density lipoprotein (HDL). Antidepressant drugs are commonly employed in treatment of mood disorders and anxiety treatment. In this study, human serum PON1 was purified using simple reproducible procedures and the effects of some antidepressant drugs on its activity were determined. It was found that mirtazapine, aripiprazole, escitalopram, and risperidone exhibited potential inhibitory properties on the purified PON1 activity with IC₅₀ values in the range of 115.50-231.00 μM and K_i values in the range of 41.66 ± 4.27 μM-276.36 ± 35.28 μM. Both risperidone and escitalopram inhibited PON1 activity competitively, while both aripiprazole and mirtazapine inhibited PON1 activity non-competitively. Chlorpromazine did not affect PON1 activity. Usage of drugs with significant biological activity may be hazardous in some cases.

Investigation of Potential Paraoxonase-I Inhibitors by Kinetic and Molecular Docking Studies: Chemotherapeutic Drugs

BACKGROUND

Metabolic processes in living organisms are closely related to the catalytic activity of enzymes. Changes in enzyme activity cause various diseases e.g., neurological, cancer, metabolic and cardiovascular. Most of the current therapeutic drugs available in clinical utilization function as enzyme inhibitors.

OBJECTIVE

The main goal of the current study to contribute to this growing drug design area (such as medication discovery and development) by investigating protein-drug interactions.

METHODS

The paraoxonase-I (PON1) enzyme was purified from human serum by using different and simple chromatographic techniques. Additionally, it was investigated inhibition effects of some chemotherapeutic drugs on the PON1.

RESULTS

The purification results for PON1 depicted a 3880.83 EU/mg proteins specific activity and the molecular weight was calculated as 43 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These drugs found to strongly inhibit PON1, with IC50 values ranging from 0.222±0.002 to 688.300±0.897 µM. Ki constants for vincristine sulfate, epirubicin hydrochloride, and doxorubicin hydrochloride were determined to be 0.235±0.032 µM, 221.400±29.270 µM, and 913.300±201.000 µM, respectively.

CONCLUSION

These drugs showed in competitive inhibition. Also, the molecular docking poses of these agents inside the catalytic sites of 1V04 and 3SRE were analysis.

A potential risk factor for paraoxonase 1: in silico and in-vitro analysis of the biological activity of proton-pump inhibitors†

Objectives

Proton-pump inhibitors (PPIs) are drugs commonly utilized by about 7% of adults in the world. Recent researches have shown that there are countless and severe side effects of these drugs. This situation has raised concern among clinicians and patients alike. The purpose of this study is to contribute the novel drug discovery and development technology and toxicology field by researching interactions of PPIs on paraoxonase 1.

Methods

In this study, the paraoxonase 1 enzyme was purified from human serum by using rapid and straightforward chromatographic techniques. Subsequently, the inhibition effects of pantoprazole, omeprazole, and esomeprazole, PPIs, were investigated on paraoxonase 1. Besides, molecular docking studies were performed to unravel the binding mechanism between the enzyme and drugs.

Key findings

All drugs showed potent inhibitory activities. IC50 of the drugs values were 54.780 ± 0.524, 86.470 ± 0.818 and 93.390 ± 0.885 mm and Ki constants were found as 39.895 ± 0.005 mm, 70.112 ± 0.010 mm and 78.868 ± 0.008 mm, respectively. The binding scores observed in silico studies were found to agree with the obtained from in-vitro experimental results.

Conclusions

We observed that the drugs decreased PON1 activity at low concentrations. The results show that adjusting the dosages of these medications is a crucial case for each patient. The physicians should more carefully interpret whether there is an essential indication before prescribing PPIs and, if there is, to approve the proper dosing for the situation.

The behaviour of some antihypertension drugs on human serum paraoxonase-1: an important protector enzyme against atherosclerosis

Objectives

Paraoxonase-1 (PON1) enzyme is related to high-density lipoprotein (HDL), which is calcium dependent. It has essential roles such as protecting LDL against oxidation and detoxification of highly toxic substances. It is a significant risk to reduce the levels of this enzyme in patients with diabetes mellitus, cardiovascular diseases, hyperthyroidism and chronic renal failure.

Methods

Here, it was reported that the purification of human serum PON1 using straightforward methods and determination of the interactions between some antihypertension drugs and the enzyme.

Key finding

It was found that these drugs exhibit potential inhibitor properties for human serum PON1 with IC50 values in the range of 131.40–369.40 μm and Ki values in the range of 56.24 ± 6.75–286.74 ± 28.28 μm. These drugs showed different inhibition mechanisms. It was determined that midodrine and nadolol were exhibited competitive inhibition, but atenolol and pindolol were exhibited non-competitive inhibition.

Conclusion

Usage of these drugs would be hazardous in some cases.

Investigation of Potential Paraoxonase-I Inhibitors by Kinetic and Molecular Docking Studies: Chemotherapeutic Drugs

Background:

Metabolic processes in living organisms are closely related to the catalytic activity of enzymes. Changes in enzyme activity cause various diseases e.g., neurological, cancer, metabolic and cardiovascular. Most of the current therapeutic drugs available in clinical utilization function as enzyme inhibitors.

Objective:

The main goal of the current study to contribute to this growing drug design area (such as medication discovery and development) by investigating protein-drug interactions.

Methods:

The paraoxonase-I (PON1) enzyme was purified from human serum by using different and simple chromatographic techniques. Additionally, it was investigated inhibition effects of some chemotherapeutic drugs on the PON1.

Results:

The purification results for PON1 depicted a 3880.83 EU/mg proteins specific activity and the molecular weight was calculated as 43 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. These drugs found to strongly inhibit PON1, with IC50 values ranging from 0.222±0.002 to 688.300±0.897 µM. Ki constants for vincristine sulfate, epirubicin hydrochloride, and doxorubicin hydrochloride were determined to be 0.235±0.032 µM, 221.400±29.270 µM, and 913.300±201.000 µM, respectively.

Conclusion:

These drugs showed in competitive inhibition. Also, the molecular docking poses of these agents inside the catalytic sites of 1V04 and 3SRE were analysis.

Gadolinium-based contrast agents: in vitro paraoxonase 1 inhibition, in silico studies

Medications show their biological effects by interaction with enzymes, which have been known to play an essential role in the pathogenesis of many diseases. Inhibition or induction of drug metabolizing enzymes has an essential place in the drug design for many kinds of diseases including cardiovascular, neurological, metabolic, and cancer. The main goal of the current study is to contribute to this growing drug design field by observing PON1-drug interactions. In recent years, the safety of gadolinium-based contrast agents (GBCAs) used in magnetic resonance imaging (MRI) has discussed. In the present study, paraoxonase 1 (PON1) enzyme was purified from human serum by simple chromatographic methods with 4095.24 EU mg^-1 protein specific activity. The inhibitory activities of gadoteric acid, gadopentetic acid, gadoxetate disodium, and gadodiamide were investigated on PON1 activity of the enzyme. IC₅₀ values were found in the range of 51.28 ± 0.14 to 285.80 ± 0.96 mM. K_i constants were found as 67.95 ± 0.60 mM, 104.97 ± 0.96 mM, 202.33 ± 1.75 mM, and 299.43 ± 2.64 mM for gadoteric acid, gadopentetic acid, gadoxetate disodium, and gadodiamide, respectively. While the inhibition types are determined as competitive of gadoxetate disodium and gadodiamide by the Lineweaver-Burk curves, it was noncompetitive for other compounds. In addition, the molecular docking analyses of gadoxetate disodium and gadodiamide were carried out to understand the binding interactions on the active site of the PON1 enzyme. The structure-activity relationship (SAR) of the drugs was established on the basis of different substituents and their positions in the compounds.

Inhibitory Effects of Usnic and Carnosic Acid on Some Metabolic Enzymes: An In vitro Study

Background:

Natural products are produced via primary and secondary metabolism in different organisms. The compounds obtained via secondary metabolism are not essential for the survival of the organism, but they can have a different value for humans.

Objective:

The objective of this study was to examine inhibitory effects of Usnic Acid (UA), a well-known lichen secondary metabolite, and Carnosic Acid (CA), the primary antioxidant compound of Rosmarinus officinalis L., on purified Human Paraoxonase, (PON1), Glutathione Reductase (GR) and Glutathione S-Transferase (GST). These enzymes have antioxidant properties and a protective effect on the oxidation of free radicals. Hence, deficiencies of such enzymes inside cells can result in a buildup of toxic substances and cause some metabolic disorders.

Methods:

UA and CA were tested in various concentrations against human GST, PON1, and GR activity in vitro and they reduced human GST, PON1, and GR activity.

Results:

UA Ki constants were calculated as 0.012±0.0019, 0.107±0.06 and 0.21±0.1 mM for GST, PON1, and GR enzymes. CA Ki constants were determined as 0.028±0.009, 0.094±0.03 and 0.79±0.33 mM, for GST, PON1, and GR enzymes. UA and CA showed competitive inhibition for GR and GST enzymes, while they exhibited non-competitive inhibition for PON1.

Conclusion:

These findings indicate that UA and CA could be useful in drug development studies.

Effect of certain non-steroidal anti-inflammatory drugs on the paraoxonase 2 (PON2) in human monocytic cell line U937

The paraoxonase gene family in humans consists of three members as PON1, PON2 and PON3. PON2 can be expressed in several tissues; however, it is not released from the cells in those tissues. PON2 is also expressed in macrophages. Firstly, the commonly used NSAIDs diclofenac sodium and tenoxicam were applied on U937 cell line, the in vitro human monocyte cell line. Than PON2 specific Lactonase activity and paraoxonase family specific arylesterase were determined. Use of Diclofenac sodium in 0.845 mM dose during 6-12 h of incubation and Tenoxicam in 0.74 mM dose during 6 h of incubation resulted in a significant decline in the lactonase activity. Diclofenac sodium didn't make any change in the arylesterase activity. On the other hand, tenoxicam decreased arylesterase activity during the use of 12 h, in 0.74 mM and 1.48 mM dose.

In vitro inhibitory effects of palonosetron hydrochloride, bevacizumab and cyclophosphamide on purified paraoxonase-I (hPON1) from human serum

In this study, we investigated the effects of the drugs, palonosetron hydrochloride, bevacizumab and cyclophosphamide, on human serum paraoxonase-I (hPON1) enzyme activity in in vitro conditions. The enzyme was purified ∼231-fold with 34.2% yield by using ammonium sulphate precipitation, DEAE-Sephadex A-50 ion-exchange chromatography and Sephadex G-200 gel-filtration chromatography from human serum. hPON1 exhibited a single protein band on the SDS polyacrylamide gel electrophoresis. The inhibition studies were performed on paraoxonase activity of palonosetron hydrochloride, bevacizumab and cyclophosphamide. Ki constants were found as 0.033±0.001, 0.054±0.003 mM and 3.419±0.518 mM, respectively. Compared to the inhibition rates of the drugs, palonosetron hydrochloride has the maximum inhibition rate. However, inhibition mechanisms of the drugs were determined as noncompetitive by Lineweaver-Burk curves.

A preliminary study of paraoxonase-1 in infected patients with an indwelling central venous catheter

OBJECTIVES

Identification of biochemical markers to diagnose bloodstream infections in patients with a central venous catheter (CVC) inserted is an active research pursuit. Paraoxonase-1 (PON1) is an enzyme participating in the innate immune system protecting against toxic substances and infectious agents. We investigated the relationships between serum PON1 alterations and the characteristics of infection in a group of patients with a CVC implant.

METHODS

Patients (n=114) who had had an inserted CVC removed because of infection or because the usefulness was at an end, and 407 healthy volunteers were recruited. In all participants we measured serum PON1 lactonase and paraoxonase activities, PON1 concentration and genetic polymorphisms, together with levels of the chemokine (C-C motif) ligand 2 (CCL2), procalcitonin and C-reactive protein (CRP).

RESULTS

Patients with an acute concomitant infection (ACI) had higher CCL2, CRP and procalcitonin concentrations than the control group, together with lower paraoxonase and lactonase activities and specific activities. The areas under the curve of the receiver operating characteristic plots for paraoxonase and lactonase specific activities in the discrimination between patients with or without and ACI were 0.81 (0.73-0.89) and 0.81 (0.71-0.89), respectively, indicating the high diagnostic accuracy of these parameters.

CONCLUSION

This preliminary study suggests that the measurement of PON1 may be useful as a tool for the diagnosis of ACI in patients with an indwelling CVC.

Impact of antibacterial drugs on human serum paraoxonase-1 (hPON1) activity: an in vitro study

OBJECTIVE

To investigate the in vitro effects of the antibacterial drugs, meropenem trihydrate, piperacillin sodium, and cefoperazone sodium, on the activity of human serum paraoxonase (hPON1).

METHODS

hPON1 was purified from human serum using simple chromatographic methods, including DEAE-Sephadex anion exchange and Sephadex G-200 gel filtration chromatography.

RESULTS

The three antibacterial drugs decreased in vitro hPON1 activity. Inhibition mechanisms meropenem trihydrate was noncompetitive while piperacillin sodium and cefoperazone sodium were competitive.

CONCLUSIONS

Our results showed that antibacterial drugs significantly inhibit hPON1 activity, both in vitro, with rank order meropenem trihydrate piperacillin sodium cefoperazone sodium in vitro.

Carbonic anhydrase activity from the gilthead sea bream (Sparus aurata) liver: the toxicological effects of heavy metals

Many studies have shown that metal ions may lead to oxidative stress in biological systems. Accordingly, DNA damage, protein modification, enzyme inhibition and activation, lipid peroxidation and many other effects may occur in living organisms. Many different formations of metal ions may enter human cells along with water, air, and various foods, and humans are negatively affected by these conditions, either directly or indirectly. These effects may cause irreversible damage to human metabolism. In this study, the toxicological effects of heavy metals on carbonic anhydrase enzyme activity from the gilthead sea bream liver were investigated. The carbonic anhydrase enzyme was purified via affinity chromatography and had a specific activity of 6775.5EUmg(-1). The kinetics and characteristic properties, such as optimum pH, stable pH, optimum temperature, activation energy (Ea), activation enthalpy (ΔH), Q10, Km, and Vmax, were determined for the purified enzyme SDS-polyacrylamide gel electrophoresis showed a single band and molecular weight of the subunit was approximately 25kDa. Cd(II), Cu(II), Ni(II) and Ag(I) inhibited the enzyme activity in vitro. The type of inhibition and Ki values for these metals were calculated from Lineweaver-Burk plots as 17.74mM, 36.20mM, 12.85mM and 0.025mM for Cd(II), Cu(II), Ni(II) and Ag(I), respectively. All the metals were noncompetitive inhibitors.

Effects of some anti-neoplastic drugs on sheep liver sorbitol dehydrogenase

Stress is an important factor for many diseases in living metabolisms. The mini pathway named as polyol is a critical junction for stress factors. This pathway has two enzymes: aldose reductase (AR) and sorbitol dehydrogenase (SDH). It is linked with some diseases such as diabetes mellitus and some cancer types. In particular, SDH is very sensitive and unstable in in vitro conditions. In this study, SDH was purified by using simple and rapid chromatographic methods such as DEAE-Sephadex and CM-Sephadex C-50 columns. Subunit and active form molecular weights were found as 39.8 kDa and 150 kDa, respectively. The in vitro effects of some antineoplastic drugs were investigated. IC(50) values were 0.025, 0.081, 0.291, 1.62, 4.86, 6.54 mM for dacarbazine, methotrexate, epirubicin hydrochloride, calcium folinate, gemcitabine hydrochloride, oxaliplatin, respectively. From these results, dacarbazine was lowest IC(50) value and it is the strongest inhibitor for liver SDH enzyme activity compared to the other drugs.

Impacts of some antibiotics on human serum paraoxonase 1 activity

Some enzymes are known to be drug target inhibitions of which can be critical for organisms. PON has a critical role to prevent atherogenesis by inhibiting lipid peroxidation. It is well known that paraoxonase 1 (PON1) plays an important function on high-density lipoprotein (HDL) structure to prevent lipid oxidation not only of low-density lipoprotein, but also of HDL itself. We investigated in vitro effects of some medical drugs on PON1 activity from human serum. Ki constants for oxytetracycline hydrochloride, netilmycin sulfate, lincomycin hydrochloride, clindamycin phosphate, and streptomycin sulfate were found as 0.2, 3.73, 18.30, 35.80, and 56.30 mM, respectively. Our results indicate that these commonly used drugs inhibit the activity of the enzyme at very low doses with different inhibition mechanisms.

The impact of heavy metals on the activity of carbonic anhydrase from rainbow trout (Oncorhynchus mykiss) kidney

Many environmental and health problems have become a consequence of contamination of soil and water by toxic heavy metals and organic pollutants in the present age of technology. Heavy metals play vital roles in enzyme activities and other metabolic events with their bioaccumulative and nonbiodegradable properties among aquatic pollutants. Metal toxicity causes irregular metallothioneins protein synthesis, renal damage, and disruption of bone structure in humans and wildlife. In this study, we investigated in vitro effects of some metals on chemical-targeted carbonic anhydrase (CA) enzyme from rainbow trout kidney. The enzyme was purified with a specific activity of 17,285 EU × mg(-1) and 31.7% yield and approximately 1800-fold using simple affinity purification method. Molecular weights of the subunit and native enzyme were estimated as 28.7 kDa and 26.9 kDa via sodium dodecyl sulfate polyacrylamide gel electrophoresis and Sephadex-G 200 column, respectively. Other kinetic properties of the enzyme were determined. Apparent K(m) , V (max) and k (cat) values were 0.40 mM, 0.097 µmol min(-1) and 15.2 s(-1) for p-nitrophenylacetate substrate, respectively. Inhibitory effects of cobalt, zinc, copper, cadmium and silver on CA activity were determined using the esterase method under in vitro conditions. IC(50) and K(i) values were calculated for metals. K(i) values for Co(2+), Zn(2+), Cu(2+), Cd(2+) and Ag(+) were 0.035, 1.2, 34.8, 103 and 257 from Lineweaver-Burk graphs, respectively. Consequently, in vitro inhibition rank order was determined as Co(2+) > Zn(2+) > Cu(2+) > Cd(2+) > Ag(+). The potential inhibitor for CA was found as Co(2+) from these results.