Suzuki Hirokazu, Ohnishi Yasuo, Furusho Yasuhide, Sakuda Shohei, Horinouchi Sueharu
Department of Biotechnology and Applied Biological Chemistry, Graduate School of Agriculture and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan.
J Biol Chem. 2006 Dec 1;281(48):36944-51. doi: 10.1074/jbc.M608103200. Epub 2006 Sep 26.
The shikimate pathway, including seven enzymatic steps for production of chorismate via shikimate from phosphoenolpyruvate and erythrose-4-phosphate, is common in various organisms for the biosynthesis of not only aromatic amino acids but also most biogenic benzene derivatives. 3-Amino-4-hydroxybenzoic acid (3,4-AHBA) is a benzene derivative serving as a precursor for several secondary metabolites produced by Streptomyces, including grixazone produced by Streptomyces griseus. Our study on the biosynthesis pathway of grixazone led to identification of the biosynthesis pathway of 3,4-AHBA from two primary metabolites. Two genes, griI and griH, within the grixazone biosynthesis gene cluster were found to be responsible for the biosynthesis of 3,4-AHBA; the two genes conferred the in vivo production of 3,4-AHBA even on Escherichia coli. In vitro analysis showed that GriI catalyzed aldol condensation between two primary metabolites, l-aspartate-4-semialdehyde and dihydroxyacetone phosphate, to form a 7-carbon product, 2-amino-4,5-dihydroxy-6-one-heptanoic acid-7-phosphate, which was subsequently converted to 3,4-AHBA by GriH. The latter reaction required Mn(2+) ion but not any cofactors involved in reduction or oxidation. This pathway is independent of the shikimate pathway, representing a novel, simple enzyme system responsible for the synthesis of a benzene ring from the C(3) and C(4) primary metabolites.
莽草酸途径包括七个酶促步骤,通过从磷酸烯醇丙酮酸和赤藓糖-4-磷酸生成莽草酸来生产分支酸,在各种生物体中普遍存在,不仅用于芳香族氨基酸的生物合成,还用于大多数生物源苯衍生物的生物合成。3-氨基-4-羟基苯甲酸(3,4-AHBA)是一种苯衍生物,是链霉菌产生的几种次级代谢产物的前体,包括灰色链霉菌产生的格氏菌素。我们对格氏菌素生物合成途径的研究导致了从两种初级代谢产物中鉴定出3,4-AHBA的生物合成途径。发现格氏菌素生物合成基因簇中的两个基因griI和griH负责3,4-AHBA的生物合成;这两个基因甚至在大肠杆菌中也能在体内产生3,4-AHBA。体外分析表明,GriI催化两种初级代谢产物L-天冬氨酸-4-半醛和磷酸二羟基丙酮之间的醛醇缩合反应,形成一种7碳产物,2-氨基-4,5-二羟基-6-酮庚酸-7-磷酸,随后由GriH将其转化为3,4-AHBA。后一反应需要Mn(2+)离子,但不需要任何参与还原或氧化的辅因子。该途径独立于莽草酸途径,代表了一种新颖、简单的酶系统,负责从C(3)和C(4)初级代谢产物合成苯环。