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首页> 外文期刊>Journal of bacteriology >Role of Acid Metabolism in Streptomyces coelicolor Morphological Differentiation and Antibiotic Biosynthesis
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Role of Acid Metabolism in Streptomyces coelicolor Morphological Differentiation and Antibiotic Biosynthesis

机译：酸代谢在天蓝色链霉菌形态分化和抗生素生物合成中的作用

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Studies of citrate synthase (CitA) were carried out to investigate its role in morphological development and biosynthesis of antibiotics in Streptomyces coelicolor. Purification of CitA, the major vegetative enzyme activity, allowed characterization of its kinetic properties. The apparent K mvalues of CitA for acetyl coenzyme A (acetyl-CoA) (32 μM) and oxaloacetate (17 μM) were similar to those of citrate synthases from other gram-positive bacteria and eukaryotes. CitA was not strongly inhibited by various allosteric feedback inhibitors (NAD+, NADH, ATP, ADP, isocitrate, or α-ketoglutarate). The corresponding gene (citA) was cloned and sequenced, allowing construction of a citA mutant (BZ2). BZ2 was a glutamate auxotroph, indicating that citA encoded the major citrate synthase allowing flow of acetyl-CoA into the tricarboxylic acid (TCA) cycle. Interruption of aerobic TCA cycle-based metabolism resulted in acidification of the medium and defects in morphological differentiation and antibiotic biosynthesis. These developmental defects of the citA mutant were in part due to a glucose-dependent medium acidification that was also exhibited by some other bald mutants. Unlike other acidogenic bald strains,citA and bldJ mutants were able to produce aerial mycelia and pigments when the medium was buffered sufficiently to maintain neutrality. Extracellular complementation studies suggested that citA defines a new stage of theStreptomyces developmental cascade.
机译：对柠檬酸合酶（CitA）进行了研究，以研究其在天蓝色链霉菌（Streptomyces coelicolor）中的形态发育和生物合成中的作用。 CitA（主要的营养酶活性）的纯化可以表征其动力学特性。乙酰辅酶A（乙酰-CoA）（32μM）和草酰乙酸（17μM）的CitA表观 K m 值类似于那些来自其他革兰氏阳性细菌和真核生物的柠檬酸合酶。各种变构反馈抑制剂（NAD + ，NADH，ATP，ADP，异柠檬酸或α-酮戊二酸）对CitA的抑制作用不强。克隆并测序了相应的基因（ citA ），从而构建了 citA 突变体（BZ2）。 BZ2是谷氨酸营养缺陷型，表明 citA 编码主要的柠檬酸合酶，使乙酰辅酶A流入三羧酸（TCA）循环。基于TCA循环的有氧代谢的中断导致培养基酸化，形态分化和抗生素生物合成方面的缺陷。 citA 突变体的这些发育缺陷部分归因于葡萄糖依赖性培养基酸化，而其他一些秃头突变体也表现出这种酸化。与其他产酸秃头菌株不同，当培养基充分缓冲以保持中性时， citA 和 bldJ 突变体能够产生气生菌丝体和色素。细胞外互补研究表明， citA 定义了链霉菌发育级联的新阶段。

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