Alcoholytic Cleavage of Polyhydroxyalkanoate Chains by Class IV Synthases Induced by Endogenous and Exogenous Ethanol
Alcoholytic Cleavage of Polyhydroxyalkanoate Chains by Class IV Synthases Induced by Endogenous and Exogenous Ethanol
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DOI：
10.1128/aem.03576-13
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发表时间：
2014-02-01
影响因子：
4.4
通讯作者：
Tsuge, Takeharu
中科院分区：
文献类型：
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作者：
Hyakutake, Manami;Tomizawa, Satoshi;Tsuge, Takeharu
产聚羟基链烷酸酯 (PHA) 的芽孢杆菌菌株表达 IV 类 PHA 合酶，由 PhaR 和 PhaC 亚基组成。表达来自蜡样芽胞杆菌菌株 YB-4 (PhaRC(YB-4)) 的 PHA 合酶的重组大肠杆菌在生长稳定期表现出异常降低的 PHA 分子量。对低分子量PHA的核磁共振分析表明，其羧基末端结构被乙醇封端，表明分子量降低是内源性乙醇诱导的PhaRC(YB-4)对PHA链进行醇解裂解的结果。在体内和体外测定中，这种断裂反应也是由外源乙醇诱导的。此外，观察到PhaRC(YB-4)对其他合酶合成的PHA链具有醇解活性。还对来自 IV 类合酶另一个亚组的巨大芽孢杆菌 (PhaRC(Bm)) 的 PHA 合酶进行了测定，结果显示对 PHA 链具有弱的醇解活性。这些结果表明，IV 类合酶可能通常具有醇解活性作为固有特征。
Polyhydroxyalkanoate (PHA)-producing Bacillus strains express class IV PHA synthase, which is composed of the subunits PhaR and PhaC. Recombinant Escherichia coli expressing PHA synthase from Bacillus cereus strain YB-4 (PhaRC(YB-4)) showed an unusual reduction of the molecular weight of PHA produced during the stationary phase of growth. Nuclear magnetic resonance analysis of the low-molecular-weight PHA revealed that its carboxy end structure was capped by ethanol, suggesting that the molecular weight reduction was the result of alcoholytic cleavage of PHA chains by PhaRC(YB-4) induced by endogenous ethanol. This scission reaction was also induced by exogenous ethanol in both in vivo and in vitro assays. In addition, PhaRC(YB-4) was observed to have alcoholysis activity for PHA chains synthesized by other synthases. The PHA synthase from Bacillus megaterium (PhaRC(Bm)) from another subgroup of class IV synthases was also assayed and was shown to have weak alcoholysis activity for PHA chains. These results suggest that class IV synthases may commonly share alcoholysis activity as an inherent feature.