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首页> 外文期刊>The Journal of Antibiotics: An International Journal >Occurrence and biosynthesis of C-demethylactinomycins in actinomycin-producing Streptomyces chrysomallus and Streptomyces parvulus
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Occurrence and biosynthesis of C-demethylactinomycins in actinomycin-producing Streptomyces chrysomallus and Streptomyces parvulus

机译：C-去甲基放线菌素在产放线菌的Chrysomallus和小链霉菌中的发生和生物合成

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摘要

Streptomyces chrysomallus and Streptomyces parvulus produce novel C-demethylactinomycins besides their normal actinomycins when fed with 3-hydroxyanthranilic acid (3-HA). The 3-HA is incorporated into pentapeptide lactone precursors in competition with the regular precursor 4-methyl-3-hydroxyanthranilic acid (4-MHA). The resultant 3-HA pentapeptide lactones can condense with each other, as well as with the continuously formed 4-MHA pentapeptide lactones giving C-demethylactinomycins lacking one or both methyl groups in their phenoxazinone chromophores. In case of C-demethylactinomyins lacking one methyl group, the condensation was shown to be regiospecific directing the 3-HA portion almost exclusively to the α-side of the phenoxazinone chromophore. As 3-HA is a weaker substrate for the 4-MHA-incorporating enzyme actinomycin synthetase I than 4-MHA, C-demethylactinomycins never exceeded 7-8% of total actinomycin formed. Surprisingly, C-demethylactinomycins (up to 0.8%) were also found in the actinomycin mixtures of unsupplemented streptomycete cultures after longer cultivation times, indicating the natural presence of 3-HA. Feeding with 3-hydroxykynurenine (3-HK) induced also formation of C-demethylactinomycins indicating that 3-HK is source of 3-HA. Analysis of tryptophan metabolites in the intracellular pools of the streptomycetes using 5- 3 H-tryptophan as radiotracer revealed formation of 4-MHA, but not of 3-HA. This indicates that intracellular 3-HK is almost exclusively converted to 3-hydroxy-4- methylkynurenine (4-MHK), which has been identified previously as direct precursor of 4-MHA. However, small amount of 3-HK leaking out from the 4-MHA pathway can be prematurely converted to 3-HA all along the cultivation of the streptomycetes resulting in the formation of natural C-demethylactinomycins.
机译：当用3-羟基邻氨基苯甲酸（3-HA）喂食时，除了正常的放线菌素外，Chrysomallus和小链霉菌还产生新的C-去甲基放线菌素。将3-HA与常规前体4-甲基-3-羟基邻氨基苯甲酸（4-MHA）竞争并入五肽内酯前体中。所得的3-HA五肽内酯可以彼此缩合，并且可以与连续形成的4-MHA五肽内酯彼此缩合，从而使C-去甲基放线菌素在其苯恶嗪酮发色团中缺少一个或两个甲基。在C-脱甲基放线菌素缺乏一个甲基的情况下，该缩合显示为区域特异性的，将3-HA部分几乎仅导向苯恶嗪酮发色团的α-侧。由于3-HA是掺入4-MHA的放线菌素合成酶I的底物比4-MHA弱，因此C-去甲基放线菌素从未超过形成的放线菌素的7-8％。出人意料的是，经过更长的培养时间后，未补充链霉菌培养物的放线菌素混合物中也发现了C-去甲基放线菌素（高达0.8％），表明3-HA的自然存在。用3-羟基犬尿氨酸（3-HK）喂养也诱导了C-去甲基放线菌素的形成，表明3-HK是3-HA的来源。使用5- 3 H-色氨酸作为放射性示踪剂分析链霉菌细胞内池中的色氨酸代谢产物，发现形成了4-MHA，但没有形成3-HA。这表明细胞内3-HK几乎完全转化为3-羟基-4-甲基犬尿氨酸（4-MHK），后者先前已被确定为4-MHA的直接前体。然而，从4-MHA途径泄漏的少量3-HK可在链霉菌的培养过程中过早地转化为3-HA，导致形成天然的C-去甲基放线菌素。

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