Wasternack C, Lippmann G, Reinbotte H
Biochim Biophys Acta. 1979 Oct 11;570(2):341-51. doi: 10.1016/0005-2744(79)90154-2.
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.
在光合有机营养生长的纤细裸藻对数中期细胞中，在粗提取物中检测到嘧啶降解酶，包括尿嘧啶还原酶、二氢尿嘧啶脱氢酶、二氢嘧啶酶和β-脲基丙酸酶。β-脲基丙酸酶（N-氨基甲酰-β-丙氨酸酰胺水解酶，EC 3.5.1.6）通过热处理、硫酸铵分级分离以及使用琼脂糖6B和DEAE-葡聚糖A-25进行色谱分离纯化了100倍。该酶遵循米氏动力学（β-脲基丙酸酶对β-脲基丙酸的Km为3.8×10⁻⁵ M，希尔系数n = 1）。其他酶学性质为：最适pH 6.25，最适温度60℃，受Mg²⁺刺激，受Cu²⁺抑制，相对分子质量约为1.5 - 2×10⁶。胸腺嘧啶降解的中间产物β-脲基异丁酸和β-脲基丙酸是β-脲基丙酸酶的竞争性底物（β-脲基丙酸酶对β-脲基异丁酸的Ki = Km为1.8×10⁻⁵ M）。β-脲基丙酸的结构类似物异丁酸和丙酸是竞争性抑制剂（β-脲基丙酸酶的Ki分别为0.3和0.16 mM）。没有迹象表明β-脲基丙酸酶在嘧啶降解中具有调节功能。
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