Xu Mingxuan, Zhu Yingmin, Jin Zhikun, Wu Huiyuan, Li Xiangfeng, Yang Yunliu, Jiao Ruisheng, Jiang Weihong, Wu Houming, Tian Wei, Bai Xiufeng, Zhao Guoping
Laboratory of Molecular Microbiology, Shanghai Institutes for Biological Science, Chinese Academy of Sciences, Shanghai 200032, China.
Sci China C Life Sci. 2006 Aug;49(4):362-9. doi: 10.1007/s11427-006-2009-y.
Apramycin is unique in the aminoglycoside family due to its octodiose moiety. However, either the biosynthesis process or the precursors involved are largely unknown. Addition of glycine, as well as serine or threonine, to the Streptomyces tenebrabrius UD2 fermentation medium substantially increases the production of apramycin with little effect on the growth of mycelia, indicating that glycine and/or serine might be involved in the biosynthesis of apramycin. The 13C-NMR analysis of [2-13C] glycine-fed (25% enrichment) apramycin showed that glycine specifically and efficiently incorporated into the only N-CH3 substituent of apramycin on the C7' of the octodiose moiety. We noticed that the in vivo concentration of S-adenosyl methionine increased in parallel with the addition of glycine, while the addition of methione in the fermentation medium significantly decreased the productivity of apramycin. Therefore, the methyl donor function of glycine is proposed to be involved in the methionine cycle but methionine itself was proposed to inhibit the methylation and methyl transfer processes a previously reported for the case of rapamycin. The 15N NMR spectra of [2-13C,15N]serine labeled apramycin indicated that serine may also act as a limiting precursor contributing to the -NH2 substituents of apramycin.
阿普拉霉素在氨基糖苷类家族中因其辛二糖部分而独具特色。然而，其生物合成过程或所涉及的前体在很大程度上尚不清楚。向黑暗链霉菌UD2发酵培养基中添加甘氨酸以及丝氨酸或苏氨酸，可显著提高阿普拉霉素的产量，而对菌丝体生长影响很小，这表明甘氨酸和/或丝氨酸可能参与阿普拉霉素的生物合成。对用[2-¹³C]甘氨酸（富集度25%）喂养的阿普拉霉素进行的¹³C-NMR分析表明，甘氨酸特异性且高效地掺入到阿普拉霉素辛二糖部分C7'上唯一的N-CH₃取代基中。我们注意到，随着甘氨酸的添加，体内S-腺苷甲硫氨酸的浓度平行增加，而在发酵培养基中添加甲硫氨酸则显著降低了阿普拉霉素的产量。因此，推测甘氨酸的甲基供体功能参与甲硫氨酸循环，但甲硫氨酸本身据推测会抑制如先前雷帕霉素案例中所报道的甲基化和甲基转移过程。[2-¹³C,¹⁵N]丝氨酸标记的阿普拉霉素的¹⁵N NMR光谱表明，丝氨酸也可能作为一种限制性前体，为阿普拉霉素的-NH₂取代基做出贡献。
