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首页> 外文期刊>Biochemistry >Crystal structure of 3-amino-5-hydroxybenzoic acid (AHBA) synthase.
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Crystal structure of 3-amino-5-hydroxybenzoic acid (AHBA) synthase.

机译：3-氨基-5-羟基苯甲酸（AHBA）合酶的晶体结构。

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摘要

The biosynthesis of ansamycin antibiotics, including rifamycin B, involves the synthesis of an aromatic precursor, 3-amino-5-hydroxybenzoic acid (AHBA), which serves as starter for the assembly of the antibiotics' polyketide backbone. The terminal enzyme of AHBA formation, AHBA synthase, is a dimeric, pyridoxal 5'-phosphate (PLP) dependent enzyme with pronounced sequence homology to a number of PLP enzymes involved in the biosynthesis of antibiotic sugar moieties. The structure of AHBA synthase from Amycolatopsis mediterranei has been determined to 2.0 A resolution, with bound cofactor, PLP, and in a complex with PLP and an inhibitor (gabaculine). The overall fold of AHBA synthase is similar to that of the aspartate aminotransferase family of PLP-dependent enzymes, with a large domain containing a seven-stranded beta-sheet surrounded by alpha-helices and a smaller domain consisting of a four-stranded antiparallel beta-sheet and four alpha-helices. The uninhibited form of the enzyme shows the cofactor covalently linked to Lys188 in an internal aldimine linkage. On binding the inhibitor, gabaculine, the internal aldimine linkage is broken, and a covalent bond is observed between the cofactor and inhibitor. The active site is composed of residues from two subunits of AHBA synthase, indicating that AHBA synthase is active as a dimer.
机译：包括利福霉素B在内的安沙霉素抗生素的生物合成涉及芳族前体3-氨基-5-羟基苯甲酸（AHBA）的合成，该前体可用作组装抗生素的聚酮骨架的起始剂。 AHBA形成的末端酶AHBA合酶是一种二聚体，吡ido醛5'-磷酸（PLP）依赖性酶，与参与抗生素糖部分生物合成的许多PLP酶具有明显的序列同源性。已确定来自地中海支链霉菌的AHBA合酶的结构达到2.0 A的分辨率，具有结合的辅因子PLP，并且与PLP和抑制剂（加巴古林）形成复合物。 AHBA合酶的整体折叠与PLP依赖性酶的天冬氨酸转氨酶家族相似，其中一个大域包含一个由α-螺旋包围的七链β-折叠，一个较小的域由一个四链反平行β组成页和四个alpha螺旋。酶的未抑制形式显示在内部醛亚胺键中与Lys188共价连接的辅因子。在结合抑制剂加巴奎林时，内部醛亚胺键断裂，并且在辅因子和抑制剂之间观察到共价键。该活性位点由来自AHBA合酶的两个亚基的残基组成，表明AHBA合酶作为二聚体具有活性。

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