Pai C H
J Bacteriol. 1971 Mar;105(3):793-800. doi: 10.1128/jb.105.3.793-800.1971.
Cell-free extracts prepared from a biotin auxotroph of Escherichia coli were active in catalyzing the synthesis of 7,8-diaminopelargonic acid, an intermediate of the biotin pathway, from 7-oxo-8-aminopelargonic acid. The product was identified on the basis of its chromatographic characteristics and its biotin activities for biotin auxotrophs of E. coli. Enzyme activity was determined in a reaction coupled with the desthiobiotin synthetase system, which is required for the conversion of 7,8-diaminopelargonic acid to desthiobiotin, and by measuring the amount of desthiobiotin formed by microbiological assay. The reaction was stimulated by l-methionine and pyridoxal-5'-phosphate. l-Methionine could not be replaced by any other amino acids tested. Pyridoxamine and pyridoxamine-5'-phosphate were as active as pyridoxal phosphate. The enzyme, presumably an aminotransferase, was demonstrable in the parent strain of E. coli and all mutant strains tested with the exception of a strain which is able to grow on diaminopelargonic acid but not on 7-oxo-8-aminopelargonic acid. Furthermore, the enzyme was repressible by biotin. The results were consistent with the hypothesis that the biosynthesis of 7,8-diaminopelargonic acid from 7-oxo-8-aminopelargonic acid is an obligatory step in the biosynthetic pathway of biotin in E. coli.
从大肠杆菌生物素营养缺陷型菌株制备的无细胞提取物，能够催化生物素途径的中间体7,8 - 二氨基壬酸从7 - 氧代 - 8 - 氨基壬酸合成。根据其色谱特征以及对大肠杆菌生物素营养缺陷型菌株的生物素活性，对产物进行了鉴定。通过与脱硫生物素合成酶系统偶联的反应来测定酶活性，该系统是7,8 - 二氨基壬酸转化为脱硫生物素所必需的，通过微生物测定法测量形成的脱硫生物素的量。该反应受到L - 甲硫氨酸和磷酸吡哆醛的刺激。L - 甲硫氨酸不能被测试的任何其他氨基酸替代。吡哆胺和磷酸吡哆胺与磷酸吡哆醛具有相同的活性。该酶可能是一种转氨酶，在大肠杆菌的亲本菌株和所有测试的突变菌株中都能检测到，但有一个菌株除外，该菌株能够在二氨基壬酸上生长，但不能在7 - 氧代 - 8 - 氨基壬酸上生长。此外，该酶可被生物素抑制。结果与以下假设一致，即从7 - 氧代 - 8 - 氨基壬酸生物合成7,8 - 二氨基壬酸是大肠杆菌生物素生物合成途径中的一个必要步骤。
