ENGINEERED BIOSYNTHESIS OF NOVEL POLYKETIDES - STEREOCHEMICAL COURSE OF 2 REACTIONS CATALYZED BY A POLYKETIDE SYNTHASE
ENGINEERED BIOSYNTHESIS OF NOVEL POLYKETIDES - STEREOCHEMICAL COURSE OF 2 REACTIONS CATALYZED BY A POLYKETIDE SYNTHASE
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DOI：
10.1021/bi00197a036
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发表时间：
1994-08-09
期刊：
影响因子：
2.9
通讯作者：
KHOSLA, C
中科院分区：
文献类型：
--
作者：
FU, H;MCDANIEL, R;KHOSLA, C
一株表达四环素聚酮合成酶(TCM PKS)和放线菌素酮还原酶(ACT KR)的基因工程菌被发现除了RM20之外，还产生两个新的(非对映异构体)芳香族聚酮，命名为RM20b和RM20c，其结构已被报道[McDaniel，R.，Ebert-Khosla，S.，Hopwood，D.A.和Khosla，C.(1993)Science 262,1546-1550]。RM20b和RM20c的光谱和体内同位素标记分析表明，它们的聚酮骨架在链长、酮还原的区域专一性和分子内第一次羟醛缩合的区域专一性方面与RM20相同。这与早期的预测一致，即PKS的基本成分--一个双功能的酮合成酶/酰基转移酶、一个链长决定因子和一个酰基载体蛋白--负责控制聚酮骨架的这些特征中的每一个[McDaniel，R.，Ebert-Khosla，S.，Hopwood，D.A.和Khosla，C.(1993)Science 262,1546-1550；McDaniel，R.，Ebert-Khosla，S.，Hopwood，D.A.和Khosla，C.(1993)J.Am化学。秒。11671-11675；Fu，H.，Ebert-Khosla，S.，Hopwood，D.A.和Khosla，C.(1994年)J.Am化学。SoC。116、4166-4170]。然而，除此之外，RM20b和RM20c还有两个不同寻常的特点。在这两个分子中，第一个六元环的SP(3)C-9和C-7上的羟基是完整的，而不是通过脱水失去的，这些羟基分别是酮还原和羟醛缩合的结果。此外，RM20b的相对产率(其中这些羟基是syn)比RM20c(其中它们是反式的)高7倍。RM20b和RM20c的新颖性表明了重组PKS的催化灵活性，并对通过操纵基因结构和组织来产生新型多酮具有令人鼓舞的意义。
A genetically engineered strain expressing the essential components of the tetracenomycin polyketide synthase (tcm PKS) along with the actinorhodin ketoreductase (act KR) was found to produce two new (diastereomeric) aromatic polyketides, designated RM20b and RM20c, in addition to RM20, whose structure was reported earlier [McDaniel, R., Ebert-Khosla, S., Hopwood, D. A., and Khosla, C. (1993) Science 262, 1546-1550]. Spectroscopic and in vivo isotopic labeling analysis of RM20b and RM20c revealed that their polyketide backbones were identical to that of RM20 with respect to chain length, regiospecificity of ketoreduction, and regiospecificity of the first intramolecular aldol condensation. This is consistent with earlier predictions that the essential components of the PKS-a bifunctional ketosynthase/acyltransferase, a chain length determining factor, and an acyl carrier protein-are responsible for controlling each of these features of the polyketide backbone [McDaniel, R., Ebert-Khosla, S., Hopwood, D. A., and Khosla, C. (1993) Science 262, 1546-1550; McDaniel, R., Ebert-Khosla, S., Hopwood, D. A., and Khosla, C. (1993) J. Am. Chem. Sec. 115, 11671-11675; Fu, H., Ebert-Khosla, S., Hopwood, D. A., and Khosla, C. (1994) J. Am. Chem. Soc. 116, 4166-4170]. In addition, however, RM20b and RM20c possess two unusual features. In both molecules the hydroxyls on sp(3) C-9 and C-7 of the first six-membered ring, which arise as a result of ketoreduction and aldol condensation, respectively, are intact, rather than being lost via dehydration. Furthermore, the relative yield of RM20b (in which these hydroxyls are syn) is 7-fold greater than that of RM20c (in which they are anti). The novelty of RM20b and RM20c is indicative of the catalytic flexibility of recombinant PKSs and has encouraging implications for the generation of novel polyketides through the manipulation of gene structure and organization.