Purification and characterization of dihydropyrimidine dehydrogenase enzyme from sheep liver and determination of the effects of some anaesthetic and antidepressant drugs on the enzyme activity

Dihydropyrimidine dehydrogenase (DPD, E.C. 1.3.1.2) was purified from sheep liver with a yield of 16.7%, purification fold of 407.5 and specific activity of 0.705 EU/mg proteins. The purification procedure consisted of ammonium sulphate fractionation, DEAE ion exchange chromatography and 2',5'-ADP Sepharose-4B affinity chromatography. The molecular weight determined by SDS-PAGE and was found 111 kDa. Optimum pH, ionic strength temperature and stable pH were determined as 8.0, 0.9 mM, 50 degrees C and 6.0, respectively. The kinetic parameters (K-m and V-max) of the enzyme were determined with NADPH as 22.97 mu M and 0.17 EU/mL, respectively. The same parameters were determined with uracil as 17.46 mu M and 0.14 EU/mL, respectively. Additionally, in vitro inhibitory effects of some antidepressant drugs including escitalopram, fluoxetine, mirtazapine, haloperidol and some anaesthetic drugs including propofol and lidocaine were investigated against DPD. In addition, IC50 values for each active drug obtained for escitalopram, fluoxetine, mirtazapine, haloperidol, propofol and lidocaine were determined as 1736.11, 13.24, 86.65, 99.03, 0.21 and 15.07 mu M, respectively.