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首页> 外文期刊>Biochemistry >Roles of Conserved Active Site Residues in the Ketosynthase Domain of an Assembly Line Polyketide Synthase
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Roles of Conserved Active Site Residues in the Ketosynthase Domain of an Assembly Line Polyketide Synthase

机译：保守的活性位点残基在装配线聚酮合酶的酮合酶结构域中的作用

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摘要

Ketosynthase (KS) domains of assembly line polyketide synthases (PKSs) catalyze intermodular trans location of the growing polyketide chain as well as chain elongation via decarboxylative Claisen condensation. The mechanistic roles of ten conserved residues in the KS domain of Module 1 of the 6-deoxyerythronolide B synthase were interrogated via site-directed mutagenesis and extensive biochemical analysis. Although the C211A mutant at the KS active site exhibited no turnover activity, it was still a competent methylmalonyl-ACP decarboxylase. The H346A mutant exhibited reduced rates of both chain translocation and chain elongation, with a greater effect on the latter half-reaction. H384 contributed to methylmalonyl-ACP decarboxylation, whereas K379 promoted C-C bond formation. S315 played a role in coupling decarboxylation to C-C bond formation. These findings support a mechanism for the translocation and elongation half-reactions that provides a well-defined starting point for further analysis of the key chain-building domain in assembly line PKSs.
机译：组装线聚酮化合物合酶（PKSs）的酮合酶（KS）域通过脱羧化Claisen缩合催化增长的聚酮化合物链的模内反式定位以及链延长。通过定点诱变和广泛的生化分析研究了6-脱氧赤藓醇内酯B合酶模块1的KS结构域中10个保守残基的机械作用。尽管在KS活性位点的C211A突变体没有显示周转活性，但它仍然是有效的甲基丙二酰-ACP脱羧酶。 H346A突变体表现出降低的链易位和链延长率，对后者的半反应影响更大。 H384促进了甲基丙二酰-ACP的脱羧作用，而K379促进了C-C键的形成。 S315在使脱羧作用与C-C键形成偶联中起作用。这些发现支持了易位和延伸半反应的机制，该机制为进一步分析装配线PKS中的关键链构建域提供了明确的起点。

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