CHARACTERIZATION OF DIHYDROPYRIMIDINASE FROM PSEUDOMONAS-STUTZERI

Dihydropyrimidinase from Pseudomonas stutzeri ATCC 17588 was purified 100-fold and characterized. It was found that dihydrouracil, dihydroth ymine and hydantoin could serve as substrates for the partially. purif ied enzyme. The K-m values for dihydrouracil, dihydrothymine and hydan toin were determined to be 19.6 mu M, 21.3 mu M and 36.4 mu M, respect ively, while their respective V-max values were 0.836 mu mol/min, 0.66 6 mu mol/min and 2.21 mu mol/min. Between pH 7.5 and 9.0, enzyme activ ity was shown to be maximal. The optimum temperature for enzyme activi ty was 45 degrees C. Using gel filtration, the molecular weight of the enzyme was calculated to be approximately 115000 Da. Metal ions were found to influence the level of enzyme activity. Dihydropyrimidinase a ctivity was stimulated by magnesium ions and inhibited by either zinc or copper ions.