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  • Title: Pyrimidine-degrading enzymes. Purification and properties of beta-ureidopropionase of Euglena gracilis.
    Author: Wasternack C, Lippmann G, Reinbotte H.
    Journal: Biochim Biophys Acta; 1979 Oct 11; 570(2):341-51. PubMed ID: 115499.
    Abstract:
    In photoorganotrophically grown, mid-log phase cells of Euglena gracilis, enzymes of pyrimidine degradation including uracil reductase, dihydrouracil dehydrogenase, dihydropyrimidinase, and beta-ureidopropionase, were detected in a crude extract. beta-Ureidopropionase (N-carbamoyl-beta-alanine amidohydrolase, EC 3.5.1.6) was purified 100-fold by heat treatment, ammonium sulphate fractionation and chromatography using Sepharose 6B and DEAE-Sephadex A-25. The enzyme follows Michaelis-Menten kinetics (Km of beta-ureidopropionase for beta-ureidopropionate 3.8 . 10(-5) M, Hill coefficient n = 1). Other enzyme properties are: pH optimum 6.25, temperature optimum 60 degrees C, stimulation by Mg2+, inhibition by Cu2+, Mr approximately 1.5--2 . 10(6). beta-Ureidoisobutyrate, the intermediate of thymine degradation, and beta-ureidopropionate are competing substrates of beta-ureidopropionase (Ki = Km of beta-ureidopropionase for beta-ureidoisobutyrate 1.8 . 10(-5) M). Structural analogues of beta-ureidopropionate, isobutyrate and propionate are competitive inhibitors (Ki of beta-ureidopropionase 0.3 and 0.16 mM, respectively). There were no indications of regulatory function of beta-ureidopropionase in pyrimidine degradation.
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