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研究了甲烷单加氧酶(MMO)、β-酮硫解酶、乙酰乙酰CoA还原酶、聚β-羟基丁酸酯(PHB)合成酶及PHB降解酶在甲烷氧化细菌胞内PHB合成途径中的催化作用.结果表明,MMO的活性随着胞内PHB的积累而持续下降,而胞内高含量的PHB有助于减缓MMO活性的降低.β-酮硫解酶控制着反应体系进入PHB循环的入口,在它和乙酰乙酰CoA还原酶的共同作用下,生成聚合单体β-羟基丁酰,二者活性在对数生长期达到峰值.PHB合成酶可将胞内的短链片段聚合,形成具有稳定高分子量的长链聚酯;当PHB合成酶活性最高时,胞内PHB浓度也随之达到峰值.同时,PHB降解酶活性随着PHB合成酶活性的增加而增加,表明在PHB循环中,PHB的合成和降解实际上是同时发生的.PHB合成酶的活性基本决定了PHB的分子量,但最终取决于PHB合成酶和PHB降解酶的共同作用.
The effects of methane monooxygenase (MMO), β-ketothiolase, acetoacetyl-CoA reductase, poly-β-hydroxybutyrate (PHB) synthase and PHB degrading enzymes on intracellular PHB synthesis of methane oxidizing bacteria The results showed that the activity of MMO decreased continuously with the accumulation of intracellular PHB while the intracellular high concentration of PHB could help to reduce the decrease of MMO activity.β-ketothiolase controls the reaction system to enter the PHB cycle , And its interaction with acetoacetyl-CoA reductase generates the monomer β-hydroxybutyryl, both of which peak in the logarithmic growth phase.PHB synthase can polymerize the intracellular short chain fragments, Form a long-chain polyester with stable high molecular weight.While the PHB synthase activity is the highest, the intracellular PHB concentration also reaches the peak value.At the same time, the PHB degrading enzyme activity increases with the increase of the PHB synthase activity, indicating that in the PHB cycle , The synthesis and degradation of PHB are actually simultaneous.PHB synthase activity basically determines the molecular weight of PHB, but ultimately depends on the combined action of PHB synthase and PHB degrading enzyme.