Macrophage Summer Spore Erwinia Fungi Carotene Synthase Interaction And Ring Dipeptide Carotenoid Biosynthesis

Carotenoids are a class of functional natural pigment presenting yellow, orange or red color. They widely exist in the nature, and have a variety of biological functions especially in protecting human health. Although carotenoids are rich in plants and microbes, extraction of a single pigment and purification of synthase complex from these organisms are rather difficult. In recent years, different carotenoids synthetic gene was cloned, relevant enzymes in the synthesis pathway was purified and several biosynthetic pathways were clarified, which provide a convenient way for research of molecular mechanism of carotenoids synthesis. These works also lay a solid foundation for isolation of a special carotenoid by microorganism fermentation and regulation of carotenoid biosynthesis process through genetic engineering. Geranylgeranyl pyrophosphate synthase(GGPP synthase) and phytoene synthase are two key enzymes of synthesis pathway of carotenoids in Erwinia uredovora. In this study, crtE encoding GGPP synthase and crtB encoding phytoene synthase were co-transformed into E.coliBL21(DE3) to construct an engineering bacterium. After induced by IPTG, expressed recombinant proteins were purified by affinity chromatography on Ni2+-Resin column and Superdex-75 gel filtration chromatography. Recombinant GGPP synthase and phytoene synthase were found to be able to form a complex.Rhodopurpurin is a kind of caroteniods, which can be accumulated in Pseudomonas fluorescens GcM5-1A. Cyclic dipeptides are also called 2,5-diketopiperazine derivatives. One of cyclic dipeptides, cyclo-(pro-tyr), can also be secreted out from P. fluorescens GcM5-1A. Previous studies indicated that there existed a relation between rhodopurpurin synthesis and cyclo-(pro-tyr) secretion. In this study, effects of cyclo-(pro-tyr) on the growth of P. fluorescens GcM5-1A and rhodopurpurin synthesis were investigated. Meanwhile, protein changes caused by this cyclic dipeptide was checked by SDS-PAGE. In addition, effect of cyclo-(pro-tyr) on expression of crtE was also studied by western blotting. The results showed that, cyclo(Pro-Val) could promote the synthesis of carotenoids and the expression of 35kDa protein and have no influence in the bacterial growth and the expression of crtE.