Purification and characterization of dihydropyrimidinase from Albizzia julibrissin
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Dihydropyrimidinase (DHPase) was purified 74-fold over the initial Albizzia extract using heat treatment, ammonium sulphate precipitation and sephadex G-200 column chromatography. its molecular mass, determined by SDS-PAGE, was approximately 56 kDa. The optimum temperatures of DHPase were 60 degrees C and 55 degrees C for dihydrouracil (DHU) and dihydrothymine (DHT), respectively. Optimum pH value of DHPasc for two substrates was found to be 9.5. The stability of DHPase was determined both in crude enzyme extract and in the sample obtained from ammonium sulphate precipitation. The effect of some metal ions on this enzyme was also examined. Km values of the enzyme for DHU and DHT were 0.33 mM and 0.37 mM, respectively. Vmax values were found as 0.15 U/mL min(-1) and 0.092 U/mL min(-1) for DHU and DHT, respectively.