Maitra U S, Sprinson D B
J Biol Chem. 1978 Aug 10;253(15):5426-30.
3-Dehydroquinate synthase was purified to homogeneity from Escherichia coli. It was found to be a single polypeptide chain of Mr = approximately 57,000. Reaction mixtures of pure enzyme and the substrate, 3-deoxy-D-arabino-heptulosonic acid 7-phosphate, were incubated for short times and treated with NaB3H4. The resulting 3-deoxyheptonic acid 7-phosphate was degraded with sodium periodate, and formic acid representing C-5 of the substrate was isolated. The presence of 3H in the formate corresponding to 15% of the enzyme was interpreted as indicating a 5-dehydro derivative of the substrate as an intermediate of the reaction. Quinic acid, resulting from reduction of 3-dehydroquinate with NaB3H4, was also isolated and degraded with periodate. The formate from C-4 of the quinate was unlabeled, indicating that 3,4-bisdehydroquinate is not an intermediate.
从大肠杆菌中纯化出了纯度达到均一的3-脱氢奎尼酸合酶。发现它是一条单多肽链，相对分子质量约为57,000。将纯酶与底物3-脱氧-D-阿拉伯庚酮糖酸7-磷酸的反应混合物短时间孵育，并用NaB₃H₄处理。所得的3-脱氧庚酮糖酸7-磷酸用高碘酸钠降解，分离出代表底物C-5的甲酸。在对应于15%酶量的甲酸盐中存在³H，这被解释为表明底物的5-脱氢衍生物是反应的中间体。用NaB₃H₄还原3-脱氢奎尼酸得到的奎尼酸也被分离出来并用高碘酸盐降解。奎尼酸C-4的甲酸盐未被标记，表明3,4-双脱氢奎尼酸不是中间体。
