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首页> 外文期刊>Biochimica et biophysica acta: international journal of biochemistry and biophysics >Insight into the activation mechanism of Escherichia coli octaprenyl pyrophosphate synthase derived from pre-steady-state kinetic analysis.
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Insight into the activation mechanism of Escherichia coli octaprenyl pyrophosphate synthase derived from pre-steady-state kinetic analysis.

机译：洞察从稳态前动力学分析得出的大肠杆菌八烯戊基焦磷酸合酶的激活机制。

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摘要

Octaprenyl pyrophosphate synthase (OPPs) catalyzes the sequential condensation of five molecules of isopentenyl pyrophosphate with farnesyl pyrophosphate to generate all-trans C40-octaprenyl pyrophosphate, which constitutes the side chain of ubiquinone. Due to the slow product release, a long-chain polyprenyl pyrophosphate synthase often requires detergent or another factor for optimal activity. Our previous studies in examining the activity enhancement of Escherichia coli undecaprenyl pyrophosphate synthase have demonstrated a switch of the rate-determining step from product release to isopentenyl pyrophosphate (IPP) condensation reaction in the presence of Triton [12]. In order to understand the mechanism of enzyme activation for E. coli OPPs, a single-turnover reaction was performed and the measured IPP condensation rate (2 s(-1)) was 100 times larger than the steady-state rate (0.02 s(-1)). The high molecular weight fractions and Triton could accelerate the steady-state rate by 3-fold (0.06 s(-1)) but insufficient to cause full activation (100-fold). A burst product formation was observed in enzyme multiple turnovers indicating a slow product release.
机译：八碳烯基焦磷酸合酶（OPPs）催化五分子异戊烯基焦磷酸与法呢基焦磷酸的顺序缩合，生成全反式C40-八烯基焦磷酸，构成泛醌的侧链。由于产品释放缓慢，长链聚异戊二烯焦磷酸合酶通常需要去污剂或其他因素才能获得最佳活性。我们先前在检查大肠杆菌十一碳烯基焦磷酸合酶活性增强中的研究表明，在存在Triton的情况下，速率决定步骤从产物释放转换为焦磷酸异戊烯基（IPP）缩合反应[12]。为了了解酶激活大肠杆菌OPP的机制，进行了单周转反应，并且测得的IPP冷凝速率（2 s（-1））比稳态速率（0.02 s（-1）大100倍。 -1））。高分子量馏分和Triton可以将稳态速率提高3倍（0.06 s（-1）），但不足以引起完全活化（100倍）。在酶的多个周转中观察到破裂的产物形成，表明产物释放缓慢。

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