从代谢流量分析角度探讨培养条件改变下对放射型根瘤茵WSH2601合成辅酶Q10的影响

分析了放射型根瘤菌(R．radiobacter)WSH2601生物合成辅酶Q10的代谢途径网络，并在溶氧条件改变和培养基中添加玉米浆条件下对辅酶Q10发酵细胞内代谢途径流量变化作定量的分析，结果表明：提高溶氧浓度(20％)5-磷酸核酮糖(RuSP)物流(r7)增加26．6，即糖酵解途径(EMP)途径向磷酸戊糖途径(HMP)转移；添加1％玉米浆r7增加17．2，EMP与HMP途径物流比值与三羧酸循环(TCA)途径物流都下降，而癸异戊烯基焦磷酸(DPP)生成物流通量(绝对值)变化都较小，即辅酶Q10的生物合成更大程度地取决于辅酶Q10生物合成途径中催化DPP的合成和4-羟基苯甲酸(PHB)与DPP的缩合反应的两种关键酶活性。6-磷酸葡萄糖(G6P)节点是辅酶Q10生物合成代谢途径的柔性节点，而丙酮酸节点是半柔性节点。细胞生物量的提高与HMP途径物流增加有关。

Effects of culture conditions on coenzyme Q10 production by Rhizobium radiobacter by metabolic flux analysis

Metabolic pathway network of CoQ 10synthesis by R. radiobacter WSH2601 were instructed. The metabolic flux and its changes were determined under the conditions of changing DO concentration and addition of 1 CSL in the medium. The results illustrated that the Ru5P flux (r 7) increased by 26.6 when increasing the DO concentration, r 7 increased by 17.2 when addition of 1 CSL. The ratio of EMP and HMP flux as well as TCA flux decreased at these two conditions. DPP flux had a little change at these two conditions. Therefore, the CoQ 10 accumulation is greatly determined by two key enzymes activities of condensation reaction between p-hydroxybenzoate acid (PHB) and decaprenyl diphosphate (DPP). The nodes of G6P, pyruvate and PEP are principal nodes in primary metabolism of CoQ 10fermentation. The flexibility of principal nodes was evaluated that the G6P node is elastic, while pyruvate node is weakly flexibility, at the condition of changing culture conditions. The increase of DCW is associated with the improvement of HMP pathway flux.