Pyrroloquinoline quinone (PQQ) has been recognized as the third class of redox cofactors in addition to the well-known nicotinamides (NAD(P)⁺) and flavins (FAD, FMN). It plays important physiological roles in various organisms and has strong antioxidant properties. The biosynthetic pathway of PQQ involves a gene cluster composed of 4–7 genes, named pqqA-G, among which pqqA is a key gene for PQQ synthesis, encoding the precursor peptide PqqA. To produce recombinant PqqA in E. coli, fusion tags were used to increase the stability and solubility of the peptide, as well simplify the scale-up of the fermentation process. In this paper, pqqA from Gluconobacter oxydans 621H was expressed in E. coli BL21 (DE3) as a fusion protein with SUMO and purified using a hexahistidine (His6) tag. The SUMO fusion protein and His6 tag were specifically recognized and cleaved by the SUMO specific ULP protease, and immobilized-metal affinity chromatography was used to obtain high-purity precursor peptide PqqA. Expression and purification of target proteins was confirmed by Tricine-SDS-PAGE. Finally, the synthesis of PQQ in a cell-free enzymatic reaction in vitro was confirmed by LC-MS.

除众所周知的烟酰胺（NAD（P）⁺）和黄素类（FAD，FMN）外，吡咯并喹啉醌（PQQ）被公认为第三类氧化还原辅助因子。它在各种生物中起着重要的生理作用，并具有很强的抗氧化性能。PQQ的生物合成途径涉及一个由4-7个基因组成的基因簇，称为pqqA-G，其中pqqA是PQQ合成的关键基因，编码前体肽PqqA。为了在大肠杆菌中生产重组PqqA ，使用融合标签增加了肽的稳定性和溶解性，并简化了发酵过程的规模化。在本文中，pqqA从氧化葡萄糖杆菌621H在大肠杆菌BL21（DE3）中作为与SUMO的融合蛋白表达，并使用六组氨酸（His6）标签纯化。SUMO特异性ULP蛋白酶可特异性识别并切割SUMO融合蛋白和His6标签，并使用固定化金属亲和色谱法获得高纯度的前体肽PqqA。通过Tricine-SDS-PAGE证实了靶蛋白的表达和纯化。最后，通过LC-MS证实了体外无细胞酶促反应中PQQ的合成。