Biosynthesis of Steroidal Saponins in Herbs / 中国实验方剂学杂志

Steroidal saponins are efficacious substances wildly existed in the herbs，and consist of glycosyl and steroid sapogenin. The biosynthesis pathways of steroidal saponins mainly include the cytosolic mevalonate （MVA） pathway and the plastidial methylerythritol 4-phosphate （MEP） pathway，with the MVA pathway as the main pathway. The key enzymes are involved in the biosynthetic pathway, including 3-hydroxy-3-methyl glutaryl coenzyme A reductase（HMGR），1-deoxy-D-xylulose 5-phosphate synthase（DXS），1-deoxy-D-xylulose-5-phosphatereduetoisomerase（DXR），farnesyl pyrophosphate synthase（FPS），squalene synthase（SS），squalene epoxidase（SE），cycloartenol synthase（CAS），cytochrome P450（CYP450），and steroidalglycosyltransferase（SGTase）. In the paper，the biosynthesis roadmap of steroidal saponins was optimized based on previous studies. According to a comprehensive analysis on studies of key enzymes for the past five years, genes, like HMGR，SS，CYP450 and UGT，were studied more，while other genes，like FPS，SE，CAS，were known less. In conclusion， current studies still focus on the primary stage，but lack direct evidence for the roles of key enzymes. This paper would provide a reference and theoretical support for subsequent studies.

Perillyl alcohol production by engineered heterologous mevalonate pathway in Escherichia coli / 生物工程学报

Perillyl alcohol, [4-isopropylene-1-cyclohexene] methanol, is a monocyclic monoterpene alcohol with special odorous similar to that of linalool and terpineol. It has application potential in pharmaceutical, daily chemical and food industries. In this study, one method for the synthesis of perillyl alcohol through the MVA pathway was studied. First, the MVA metabolic pathway originated from Enterococcus faecalis was constructed in Escherichia coli to synthesize limonene. Limonene was further transformed to perillyl alcohol by the hydroxylation of cytochrome P450 alkane hydroxylase. Furthermore, the shake flask fermentation condition of the engineered E. coli strain was optimized. The results showed that the engineered E. coli could produce about 50.12 mg/L perillyl alcohol through MVA pathway using glucose as raw material. In this study, the method of the MVA pathway for perillyl alcohol synthesis was constructed successfully in engineered E. coli, which provides both theoretical and technical support for terpenoids biosynthesis.