Mueller E J, Meyer E, Rudolph J, Davisson V J, Stubbe J
Department of Chemistry, Massachusetts Institute of Technology, Cambridge 02139.
Biochemistry. 1994 Mar 1;33(8):2269-78. doi: 10.1021/bi00174a038.
Conversion of aminoimidazole ribonucleotide (AIR) to 4-carboxyaminoimidazole ribonucleotide (CAIR) in Escherichia coli requires two proteins, PurE and PurK, previously thought to be subunits of a single enzyme, AIR carboxylase. Past studies revealing an ATP requirement for this reaction (Meyer et al., 1992), in conjunction with present studies, reveal that PurE and PurK possess independent catalytic activities. PurK is shown, by NMR spectroscopy, to catalyze the conversion of AIR in the presence of HCO3- and ATP to ADP, P(i), and the carbamate of AIR (designated N5-CAIR). PurE has been shown by NMR spectroscopy and kinetic analysis, to catalyze the reversible conversion of N5-CAIR and CAIR. N5-CAIR has a half-life of 0.9 min at pH 7.8 and 30 degrees C. Thus, two new enzymatic activities and a new intermediate have been discovered in the de novo purine biosynthetic pathway of E. coli.
在大肠杆菌中，氨基咪唑核糖核苷酸（AIR）转化为4-羧基氨基咪唑核糖核苷酸（CAIR）需要两种蛋白质，即PurE和PurK，它们以前被认为是单一酶——AIR羧化酶的亚基。过去的研究揭示了该反应对ATP的需求（Meyer等人，1992年），结合目前的研究表明，PurE和PurK具有独立的催化活性。通过核磁共振光谱法显示，PurK在HCO3-和ATP存在的情况下催化AIR转化为ADP、无机磷酸（P(i)）和AIR的氨基甲酸酯（称为N5-CAIR）。通过核磁共振光谱法和动力学分析表明，PurE催化N5-CAIR和CAIR的可逆转化。N5-CAIR在pH 7.8和30℃下的半衰期为0.9分钟。因此，在大肠杆菌的嘌呤从头生物合成途径中发现了两种新的酶活性和一种新的中间体。
