3-Amino-5-hydroxybenzoic Acid Synthase, the Terminal Enzyme in the Formation of the Precursor of mC7N Units in Rifamycin and Related Antibiotics
作者:Chun-Gyu Kim、Tin-Wein Yu、Craig B. Fryhle、Sandeep Handa、Heinz G. Floss
DOI:10.1074/jbc.273.11.6030
日期:1998.3
5-deoxy-5-amino-3-dehydroshikimic acid, has been purified to homogeneity from Amycolatopsis mediterranei, the encoding gene has been cloned, sequenced, and overexpressed in Escherichia coli. The recombinant enzyme, a (His)6 fusion protein, as well as the native one, are dimers containing one molecule of pyridoxal phosphate per subunit. Mechanistic studies showed that the enzyme-bound pyridoxal phosphate forms a Schiff's
类似于利福霉素B的安沙霉素抗生素的生物合成涉及通过the草酸酯途径的新型变异形式形成3-氨基-5-羟基苯甲酸(AHBA)。然后,AHBA用作组装聚酮化合物的起始单元,该聚酮化合物最终连接回到AHBA的氨基上,形成大内酰胺环。AHBA形成的末端酶可催化5-deoxy-5-amino-3-dehydroshikimic acid的芳构化,已从地中海支链淀粉中纯化至同质,已在大肠杆菌中克隆,测序和过表达编码基因。重组酶是一种(His)6融合蛋白,也是天然的一种,是每个亚基中含有一个磷酸吡ido醛分子的二聚体。机理研究表明,酶结合的吡ido醛磷酸盐形成席夫氏 带有5-脱氧-5-氨基-3-脱氢shi草酸的氨基的α-碱基,并且催化底物的α,β-脱水和立体有择的1,4-烯化。Mediterranei基因组中编码AHBA合酶的基因失活会导致利福霉素的形成丢失;当突变体补充AHBA后,恢复了抗生素的生产。