Abstract：
When hypoxanthine was utilized as the activator for the salvage pathway in cAMP synthesis, xanthine oxidase would generate in quantity leading to low hypoxanthine conversion ratios and cell viability. To enhance cAMP salvage synthesis, fermentations with citrate/luteolin and hypoxanthine coupling added were conducted in a 7 L bioreactor and then multiple physiological indicators of fermentation with luteolin addition were assayed. Due to hypoxanthine feeding, cAMP productivity reached 0.066 g/(L·h) with 43.5% higher than control, however, cAMP synthesis, cell growth and glucose uptake all ceased at 50 h which was shortened by 22 h in comparison to control. The addition of citrate resulted in the cessation of fermentation at 61 h, on the contrary, owing to luteolin addition, cAMP fermentation performance was enhanced significantly during the whole fermentation period (72 h) with higher hypoxanthine conversion ratios and cAMP contents when compared with citrate and only hypoxanthine added batches. Multiple physiological indicators revealed that luteolin inhibited xanthine oxidase activity reducing hypoxanthine decomposition and ROS generation. ATP/AMP, NADH/NAD+ and NADPH/NADP+ were significantly increased especially at the late phase. Moreover, HPRT, PUP expression contents and corresponding gene transcription levels were also elevated. Luteolin could inhibit xanthine oxidase activity and further decrease hypoxanthine decomposition and ROS generation leading to higher hypoxanthine conversion and less cell damage for cAMP salvage synthesis efficiently.
摘要：
当次黄嘌呤被用作cAMP合成中补救途径的激活剂时，黄嘌呤氧化酶将大量产生，导致次黄嘌呤转化率和细胞活力低。为了增强cAMP抢救合成，在7L生物反应器中添加柠檬酸盐/木犀草素和次黄嘌呤偶联进行发酵，然后测定添加木犀草素发酵的多个生理指标。由于次黄嘌呤的喂养，cAMP生产率达到0.066g/(L·h)，比对照高43.5%，然而,cAMP合成，细胞生长和葡萄糖摄取均在50小时停止，与对照组相比缩短了22小时。添加柠檬酸盐导致发酵在61小时停止，相反,由于添加木犀草素，与柠檬酸盐和仅添加次黄嘌呤的批次相比，在整个发酵期间（72h），次黄嘌呤转化率和cAMP含量更高，cAMP发酵性能显着提高。多种生理指标显示木犀草素抑制黄嘌呤氧化酶活性,减少次黄嘌呤分解和ROS生成。ATP/AMP,NADH/NAD+和NADPH/NADP+在晚期显著增加。此外，HPRT,PUP表达含量和相应的基因转录水平也升高。木犀草素可以抑制黄嘌呤氧化酶的活性，并进一步减少次黄嘌呤的分解和ROS的产生，从而有效地提高次黄嘌呤的转化率和减少cAMP挽救合成的细胞损伤。
