Aygul, Imdat; Ozdemir, Hasan; Ciftci, Mehmet

The inhibitory effects of certain drugs on dihydropyrimidine dehydrogenase from the bovine liver have been investigated. Dihydropyrimidine dehydrogenase [5, 6-dihydrouracil: NADP+ oxidoreductase, EC 1.3.1.2; DPD] enzyme was purified from the bovine liver. The purification was performed by preparation of homogenate, ammonium sulphate precipitation, and affinity chromatography. Moreover, some important modifications were made in the purification procedure. Purification of bovine liver DPD enzyme was obtained with a yield of 12.5%. SDS polyacrylamide gel electrophoresis was performed after the purification of the enzyme, and the electrophoretic pattern is discussed in this article. In addition, the effects of certain drugs on bovine liver dihydropyrimidine dehydrogenase enzyme activity were investigated. Oxytetracycline, ciprofloxacin, ceftazidime, cefoperazone, amikacin, ornidazole, metronidazole, cefuroxime, cefepime, ampicillin, and amoxicillin, were used as drugs. All the drugs indicated the inhibitory effects on the enzyme. IC50 values of the drugs were determined by plotting activity % vs [I]. IC50 values of oxytetracycline, ciprofloxacin, ceftazidime, cefoperazone, amikacin, ornidazole, metronidazole, cefuroxime, cefepime, ampicillin, and amoxicillin 0.030, 0.046, 0.140, 0.610,1.820, 2.500, 3.600, 4.330, 4.370, 4.920, and 6.300, mM; the Ki constants were 0.050±0.01,0.090± 0.06, 0.130±0.045, 0.185±0.057, 2.010±0.55, 2.096±1.06, 2.115±1.00, 2.700±0.56, 3.730±1.48, 5.240±1.04, and 9.570±2.84, mM for bovine liver DPD, respectively. Ki constants for dihydropyrimidine dehydrogenase were determined by Lineweaver-Burk graphs. All drugs showed non-competitive inhibition patterns.

Sarikaya, S. Beyza Ozturk; Sisecioglu, Melda; Cankaya, Murat; Gulcin, Ilhami; Ozdemir, Hasan

Lactoperoxidase (LPO) catalyzes the oxidation of numerous of organic and inorganic substrates by hydrogen peroxide. It has very vital activity in the innate immune system by decreasing or stopping the activation of the bacteria in milk and mucosal secretions. This study's purpose was to investigate in vitro effect of some phenolic acids (ellagic, gallic, ferulic, caffeic, quercetin, p-coumaric, syringic, catechol and epicatechin) on the purified LPO. This enzyme was purified from milk by using different methods such as Amberlite CG-50 resin, CM-Sephadex C-50 ion-exchange and Sephadex G-100 gel filtration chromatography. LPO was purified 28.7-fold with a yield of 20.03%. We found phenolic acids have inhibition effects on bovine LPO enzyme to different concentrations. Our study showed lower concentrations of caffeic acid, ferulic acid and quercetin exhibited much higher inhibitory effect on enzyme, so these three of them were clearly a more potent inhibitor than the others were. All of compounds were non-competitive inhibitors.