| Popis: |
Paraoxonase 1 (PON1) is a calcium-dependent enzyme whose physiological substrate and physiological role are still the subject of many research efforts. The reduced catalytic activity of PON1 in humans has been demonstrated in many pathological conditions such as diabetes, chronic kidney or liver disease, hyperlipoproteinemia, Alzheimer's and thyroid diseases. Mammalian PON1 possesses arylesterase, lactonase and phosphotriestrase activity and it is able to hydrolyse a very broad spectrum of esters, like some xenobiotics, endogenous proantibiotics and lactones. The aim of this work was to determine whether carbamate esters affect a G2E6 variant of recombinant PON1, expressed and purified in the Escherichia coli bacterial system. We tested carbamates of different application fields ; bambuterol in use as bronchodilator, carbofuran as pesticide, physostigmine as a drug for treating glaucoma and delayed gastric empting, and Ro(02-0683) in use for BChE phenotyping. The impact of carbamates on PON1 activity was expressed as an enzyme-inhibitor dissociation constant Ki, while 1/Ki represents the enzyme affinity towards the tested carbamate. Enzyme activity was measured spectrophotometrically at 412 nm at 25 °C in 50 mM TrisHCl buffer, pH 8.0, containing 1 mM CaCl2, and using thiophenyacetate (TPA) as a substrate for PON1’s arylesterase activity. Evaluation of the Ki constants demonstrated that all carbamates compete with TPA for binding to the active site of the enzyme. PON1 displayed almost the same affinity towards Ro(02-0683), bambuterol and physostigmine, while it was about five times higher towards carbofuran. Generally, affinity of PON1 towards carbamates was 2-10 times lower compared to that of TPA. In conclusion, carbamates could reduce the level of PON1 activity, which should be kept in mind especially in conditions characterized by reduced PON1 level. Acknowledgment: Work was supported by HrZZ (Grant No.4307) and Croatian-Slovenian bilateral project 2016-2017. |
