Yilmaz, Aycan; Dilek, Esra

Background: Paraoxonase (PON; arilesterase, [EC 3.1.8.1]) is an enzyme from the group arilesterases (ARE). This enzyme is capable of hydrolyzing paraoxone which is the active metabolite of parathion, an organic phosphorus insecticide. PON activity was found to be low in individuals prone to development of atherosclerosis such as diabetes, familial hypercholesterolemia and kidney disorders. It was noted that PON enzyme activity decreases in relation to age increase in adults. PON enzyme activity is approximately half of that in newborns and premature babies. Approximately one year after birth, it reaches the adult level. It can be said that PON1 has significant role on living organisms. For this reason, many studies on interactions of PON-drugs are needed. Objective: In this article, our aim is to investigate in vitro effects of four pharmaceutically active agents (fosfomycin, cefuroxime axetil, cefaclor monohydrate, and cefixime) which are often used in patients after surgery on human serum paraoxanase-I (PON1) enzyme activity. Methods: In this article, we purify paraoxonase-I enzyme from human serum by using ammonium sulfate precipitation (in the range of 60-80%), ion exchange and gel filtration chromatography. We use electrophoresis to check the purity of the enzyme. We investigate the paraoxonase activity of the enzyme at 412 nm the inhibition effects of the active substances. Paraoxone is used as the substrate. Activity measurements arw made at different inhibitor concentrations related to inhibitor studies and % Activity- [I] graphs are drawn for drug active substances. Lineweaver-Burk graphics are used to determine the Ki constants. Finally, to determine the types of inhibition we interpret these graphs. Results: The active agents used after surgery decreased the PON1 enzyme activity. They showed different inhibition mechanism. The inhibition mechanism of fosfomycin and cefaclor monohydrate was noncompetitive, cefixime was uncompetitive and cefuroxime axetil was a competitive inhibitor. The IC50 values for fosfomycin, cefuroxime axetil, cefaclor monohydrate, and cefixime were calculated to be 31.5 mM, 1.03 mM, 4.18 mM and 0.781 mM, respectively, and the Ki constants were determined to be 27.98 ± 12.25 mM, 2.20 ± 0.22 mM, 4.81 ± 2.25 mM and 1.12 ± 0.32 mM, respectively. The IC50 and Ki values showed that cefixime active agent has the maximum inhibition. Conclusion: In this study, we have detected that cefuroxime axetil inhibited competitively in vitro paraoxonase activity of this enzyme. According to this information, we thought that cefuroxime axetil linked to the active site of the enzyme. Fosfomycin and cefaclor monohydrate can be attached with amino acids out of the active site of the enzyme because they inhibit enzyme noncompetitively. Cefixime can be attached only to the enzyme-substrate complex because it inhibits enzyme uncompetitively.

Türketş, Cüneyt

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 0.222T ± 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.

Dileka, Esra; Polat, Muhammet F.

We studied in vitro effects of three different drugs (ibuprofen, meloxicam and methotrexate) which are often used in rheumatoid arthritis (RA) treatment on human serum paraoxanase1 (PON1) enzyme activity. The drugs used in RA treatment decreased the in vitro PON1 activity. The inhibition mechanism of ibuprofen and methotrexate were noncompetitive whereas meloxicam was a competitive inhibitor. The IC50 values for ibuprofen, meloxicam and methotrexate were calculated to be 0.35 mM, 0.10 mM, and 0.18 mM, respectively, and the Ki constants were calculated to be 0.890 mM, 0.125 mM, and 0.260 mM, respectively. The IC50 and Ki values showed the maximum inhibition of meloxicam drugs. We propose a prediction scheme for the interaction of meloxicam with the PON1 active site because we thought that meloxicam interacts with the amino acids which are in the PON1 enzyme active site. The results we found showed that these drugs which are often used in RA treatment in vitro inhibit the activity of the enzyme with different inhibition mechanisms at low doses.

Aydin, Suleyman; Aydin, Suna; Eren, Mehmet Nesimi; Sahin, Ibrahim

Apelins are a peptide hormone known as the ligand for the G protein-coupled APJ receptor. There are many different forms of apelin in the circulation. Apelins and their receptors are expressed in the central nervous system, including the hypothalamus, and in numerous other peripheral tissues. These peptides are also synthesized in and secreted from the adipose tissues. Additionally, apelins were immunohistochemically shown to be synthesized in smooth muscle cells in the media of the left internal mammary artery (LIMA) and the saphenous vein, fibroblast cells in the media of the aorta and endothelial cells of the intima. Similarly, it was recently reported that the enzyme linked immunoassay (ELISA) measurements of apelins were similar to its immunohistochemical data in the tissues of the aorta and left internal mammary artery. Apelins which are rapidly eliminated from the circulation have a half life of less than eight minutes. The normal concentration of apelins in the human plasma ranges between 1.3 ng/mL and 246±0.045 ng/mL. Apelins serve important functions in food intake, vasopressin (anti-diuretic hormone: ADH) and histamine release, gastric acid, bicarbonate secretion and insulin secretion, diuresis, cell proliferation, angiogenesis, glucose-fluid balance and regulation of gastrointestinal motility and cardiovascular system. Therefore, this review aims to focus on the potential role of the apelin system in the balance of the cardiovascular system.

Coban, T. Abdulkadir; Senturk, Murat; Ciftci, Mehmet; Kufrevioglu, O. Irfan

In this study, we investigated inhibitory effects of some metal ions on human erythrocyte glutathione reductase. For this purpose, initially human erythrocyte glutathione reductase was purified 1051-fold in a yield of 41% by using 2′, 5′-ADP Sepharose 4B affinity gel and Sephadex G-200 gel filtration chromatography. SDS polyacrylamide gel electrophoresis was done in order to control the purification of enzyme. SDS polyacrylamide gel electrophoresis showed a single band for enzyme. A constant temperature (4°C) was maintained during the purification process. Enzyme activity was determined with the Beutler method by using a spectrophotometer at 340 nm. Hg2+, Cd2+, Pb2+, Cu2+, Fe 3+ and Al3+ exhibited inhibitory effects on the enzyme in vitro. Ki constants and IC50 values for metal ions were determined by Lineweaver-Burk graphs and plotting activity % vs. [I]. IC 50 values of Pb2+, Hg2+, Cu2+, Cd2+ , Fe3+ and Al3+ were 0.011, 0.020, 0.0252, 0.0373, 0.209 and 0.229 mM, and the Ki constants 0.0254±0.0027, 0.0378±0.0043, 0.0409±0.0048, 0.0558±0.0083, 0.403±0.043 and 1.137±0.2 mM, respectively. While Pb2+, Hg2+, Cd2+ and Fe3+ showed competitive inhibition, others displayed noncompetitive inhibition.