Two types of coumarins-specific enzymes complete the last missing steps in pyran- and furanocoumarins biosynthesis

Pyran- and furanocoumarins are key representatives of tetrahydropyrans and tetrahydrofurans, respectively, exhibiting diverse physiological and medical bioactivities. However, the biosynthetic mechanisms for their core structures remain poorly understood. Here we combined multiomics analyses of biosynthetic enzymes in Peucedanum praeruptorum and in vitro functional verification and identified two types of key enzymes critical for pyran and furan ring biosynthesis in plants. These included three distinct P. praeruptorum prenyltransferases (PpPT1-3) responsible for the prenylation of the simple coumarin skeleton 7 into linear or angular precursors, and two novel CYP450 cyclases (PpDC and PpOC) crucial for the cyclization of the linear/angular precursors into either tetrahydropyran or tetrahydrofuran scaffolds. Biochemical analyses of cyclases indicated that acid/base-assisted epoxide ring opening contributed to the enzyme-catalyzed tetrahydropyran and tetrahydrofuran ring refactoring. The possible acid/base-assisted catalytic mechanisms of the identified cyclases were theoretically investigated and assessed using site-specific mutagenesis. We identified two possible acidic amino acids Glu303 in PpDC and Asp301 in PpOC as vital in the catalytic process. This study provides new enzymatic tools in the epoxide formation/epoxide-opening mediated cascade reaction and exemplifies how plants become chemically diverse in terms of enzyme function and catalytic process.

Embolism techniques adopted in treating multiple trauma accompanied with hemorrhagic shock / 中国普通外科杂志

Objective To study the effective hemostatic method for treating multiple trauma accompanied with hemorrhagic shock to increase the existence rate. Methods In treating 5 patients of multiple tauma accompanied with hemorrhagic shock, We used radiological embolism to injuried parenchymatous organs and injuried vessels to arrest the bleeding at first. After shock recovered, prompt exploration was made to repair injuried hollow viscus. Results After embolism and bleeding arrested, shocks in all 5 patients were corrected in short time; and no serious active hemorrhage was found after abdominal operation to repair the hollow viscus. All 5 patients survived after the operation. Conclusions The radiological embolism is simple,and has the little trauma and a good hemostatic effect,and needs short time. The method for treating multiple trauma can improve the salvage rate of multiple trauma accompanied with hemorrhagic shock and fit the treatment principle of multiple trauma.