The Streptomyces tendae Tu901 L-lysine 2-aminotransferase catalyzes the initial reaction in nikkomycin D biosynthesis
The Streptomyces tendae Tu901 L-lysine 2-aminotransferase catalyzes the initial reaction in nikkomycin D biosynthesis
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DOI：
10.1046/j.1432-1327.1998.2540347.x
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发表时间：
1998-06-01
期刊：
影响因子：
--
通讯作者：
Bormann, C
中科院分区：
文献类型：
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作者：
Bruntner, C;Bormann, C
蛋白P8先前被鉴定为推定的尼可霉素生物合成蛋白。从链霉菌Tendae Tii 901尼克霉素基因簇中克隆了编码P8蛋白的基因（nikC）并进行了测序。通过插入卡那霉素抗性盒使nikC基因失活;突变体不产生具有生物活性的尼可霉素I、J、X和Z，但积累核苷部分尼可霉素C-X和C-Z。突变体通过从载体pIJ 702的mel启动子表达的nikC与尼可霉素生产（I，J，X，Z）互补。此外，尼可霉素阴性表型通过向培养基中加入吡啶甲酸（尼可霉素（尼可霉素D）的肽基部分的前体）而逆转。nikC基因在大肠杆菌中表达，并在酶水平上鉴定和表征。NikC编码L-赖氨酸2-氨基转移酶，并且仅在尼可霉素生产者中检测到活性，并且其存在与尼可霉素生产相关。nikC失活突变体以L-赖氨酸作为唯一的氮和碳源生长，表明L-赖氨酸2-氨基转移酶不是赖氨酸催化剂所必需的。我们的研究结果确定了nikC编码的L-赖氨酸2-氨基转移酶作为尼可霉素生物合成酶，催化尼可霉素D生物合成中的初始反应。NikC蛋白属于吡哆胺或磷酸吡哆醛依赖性脱氢酶和氨基转移酶的新家族，其中一些参与双脱氧和脱氧氨基糖的生物合成。
Protein P8 was previously identified as a putative nikkomycin biosynthesis protein. The gene (nikC) encoding protein P8 was cloned from the Streptomyces tendae Tii901 nikkomycin gene cluster and sequenced. The nikC gene was inactivated by inserting a kanamycin resistance cassette; the mutant did not produce the biologically active nikkomycins I, J, X, and Z, but accumulated the nucleoside moieties nikkomycins C-X and C-Z. The mutant was complemented to nikkomycin production (I, J, X, Z) by nikC expressed from the mel promoter of the vector pIJ702. Furthermore, the nikkomycin-negative phenotype was reversed by the addition of picolinic acid, a precursor of the peptidyl moiety of nikkomycins (nikkomycin D), into the culture medium. The nikC gene was expressed in Escherichia coli and identified and characterized at the enzyme level. NikC encodes an L-lysine 2-aminotransferase, and the activity was exclusively detected in nikkomycin producers and its presence correlated to nikkomycin production. The nikC-inactivated mutant grew with L-lysine as sole source of nitrogen and carbon, indicating that L-lysine 2-aminotransferase is not required for lysine catabolism. Our results identified the nikC-encoded L-lysine 2-aminotransferase as the nikkomycin biosynthetic enzyme that catalyzes the initial reaction in nikkomycin D biosynthesis. The NikC protein belongs to a novel family of pyridoxamine or pyridoxal-phosphate-dependent dehydrases and aminotransferases, some of which are involved in dideoxy- and deoxy-aminosugar biosynthesis.