C14-functionalized steroids enabled diverse biological activities in anti-gonadotropin and anticancer therapy. However, access to C14-functionalized steroids was impeded by the deficiency of chemical synthetic methods. Recently, several membrane-bound fungal cytochrome P450s (CYPs) have been identified with steroid C14α-hydroxylation activity. However, the lack of efficient heterologous overexpression strategy hampered their further characterization and molecular engineering. In the present study, sequences of fungi-derived CYP genes encoding putative 14α-hydroxylase were selected and bioinformatically analyzed. Substitution of the N-terminal hydrophobic helix by a soluble maltose binding protein tag significantly enhanced the soluble expression level in Escherichia coli. A novel CYP originated from Bipolaris oryzae was discovered with high steroidal C14α-hydroxylation activity when coupled with the redox partner CPR
Abstract The abnormality of immune regulation plays a critical role in the pathogenesis of cancer; the underlying mechanism has not been fully understood yet. This study aims to investigate the role of cancer specific T helper (Th)2 response in the inhibition of colon cancer (Cca) cell growth. The results showed that with Cca cell (CT26 cell) extracts as an antigen, the Cca-extract specific Th2 response was induced in the Cca-bearing mice. The Cca mass size was significantly reduced, or radically disappeared (5 out of 10; or 50%); the survival rate was markedly improved in mice immunized with Cca-extract, but not in those immunized with another tumor cell (U87 cell) extracts or to bovine serum albumin. The immunization with Cca-extract also induced Cca cell apoptosis and converted the intra-Cca Tregs to T helper (Th) 9 cells. In conclusion, Cca-specific Th2 responses inhibit Cca growth in a mouse model via inducing Cca cell apoptosis and converting intra-Cca Tregs to Th9 cells.
Abstract Steroid-based drugs are now mainly produced by the microbial transformation of phytosterol, and a two-step bioprocess is adopted to reach high space–time yields, but byproducts are frequently observed during the bioprocessing. In this study, the catabolic switch between the C19- and C22-steroidal subpathways was investigated in resting cells of Mycobacterium neoaurum NRRL B-3805, and a dose-dependent transcriptional response toward the induction of phytosterol with increased concentrations was found in the putative node enzymes including ChoM2, KstD1, OpccR, Sal, and Hsd4A. Aldolase Sal presented a dominant role in the C22 steroidal side-chain cleavage, and the byproduct was eliminated after sequential deletion of opccR and sal . Meanwhile, the molar yield of androst-1,4-diene-3,17-dione (ADD) was increased from 59.4 to 71.3%. With the regard of insufficient activity of rate-limiting enzymes may also cause byproduct accumulation, a chromosomal integration platform for target gene overexpression was established supported by a strong promoter L2 combined with site-specific recombination in the engineered cell. Rate-limiting steps of ADD bioconversion were further characterized and overcome. Overexpression of the kstD1 gene further strengthened the bioconversion from AD to ADD. After subsequential optimization of the bioconversion system, the directed biotransformation route was developed and allowed up to 82.0% molar yield with a space–time yield of 4.22 g·L −1 ·day −1 . The catabolic diversion elements and the genetic overexpression tools as confirmed and developed in present study offer new ideas of M. neoaurum cell factory development for directed biotransformation for C19- and C22-steroidal drug intermediates from phytosterol. Key points • Resting cells exhibited a catabolic switch between the C19- and C22-steroidal subpathways. • The C22-steroidal byproduct was eliminated after sequential deletion of opccR and sal. • Rate-limiting steps were overcome by promoter engineering and chromosomal integration.
Abstract l ‐homoserine is an important platform compound of many valuable products. Construction of microbial cell factory for l ‐homoserine production from glucose has attracted a great deal of attention. In this study, l ‐homoserine biosynthesis pathway was divided into three modules, the glucose uptake and upstream pathway, the downstream pathway, and the energy supply module. Metabolomics of the chassis strain HS indicated that the supply of ATP was inadequate, therefore, the energy supply module was firstly modified. By balancing the ATP supply module, the l ‐homoserine production increased by 66% to 12.55 g/L. Further, the results indicated that the upstream pathway was blocked, and increasing the culture temperature to 37°C could solve this problem and the l ‐homoserine production reached 21.38 g/L. Then, the downstream synthesis pathways were further strengthened to balance the fluxes, and the l ‐homoserine production reached the highest reported level of 32.55 g/L in shake flasks. Finally, fed‐batch fermentation in a 5‐L bioreactor was conducted, and l ‐homoserine production could reach to 119.96 g/L after 92 h cultivation, with the yield of 0.41 g/g glucose and productivity of 1.31 g/L/h. The study provides a well research foundation for l ‐homoserine production by microbial fermentation with the capacity for industrial application.
