Cloning and Expression Analysis of a Chalcone isomerase (CnCHI) Gene from Chamaemelum nobile

Molecular cloning and in silico analysis of chalcone isomerase from Polygonum minus

BACKGROUND

Chalcone isomerase (CHI; EC 5.5.1.6) is one of the key enzymes in the flavonoid biosynthetic pathway that is responsible for the intramolecular cyclization of chalcones into specific 2S-flavanones.

METHODS AND RESULTS

In this study, the open reading frame (ORF) of CHI was successfully isolated from the cDNA of Polygonum minus at 711-bp long, encoding for 236 amino acid residues, with a predicted molecular weight of 25.4 kDa. Multiple sequence alignment and phylogenetic analysis revealed that the conserved residues (Thr50, Tyr108, Asn115, and Ser192) in the cleft of CHI enzyme group active site are present in PmCHI protein sequence and classified as type I. PmCHI comprises more hydrophobic residues without a signal peptide and transmembrane helices. The three-dimensional (3D) structure of PmCHI predicted through homology modeling was validated by Ramachandran plot and Verify3D, with values within the acceptable range of a good model. PmCHI was cloned into pET-28b(+) plasmid, expressed in Escherichia coli BL21(DE3) at 16 °C and partially purified.

CONCLUSION

These findings contribute to a deeper understanding of the PmCHI protein and its potential for further characterization of its functional properties in the flavonoid biosynthetic pathway.

Enhancing the sustainability of KsdD as a biocatalyst for steroid transformation by immobilization on epoxy support

The Δ1-dehydrogenation of 3-ketosteroid substrates is a crucial reaction in the production of steroids. Although 3-ketosteroid Δ1-dehydrogenase (KsdD) catalyzes this reaction with high efficiency and selectivity, the low stability and high cost of the purified enzyme catalyst have limited its industrial application. In this study, an epoxy support was used to evaluate the covalent immobilization of KsdD from Pimelobacter simplex, and the best androsta-1,4-diene-317-dione (ADD) production was achieved after optimized immobilization of KsdD enzyme in 1.5 M NaH₂PO₄- Na₂HPO₄ buffer (pH 6.5) for 12 h at 25 °C. The immobilized KsdD exhibited higher tolerance toward 20 % methanol. The dehydrogenation reaction reached a conversion efficiency of up to 90.0 % in 2 h when using 0.6 mg/mL of 4-androstene-317-dione (AD). The W299A and W299 G mutants of KsdD were also immobilized, and both showed the better catalytic performance with higher k_cat/K_M values compared with the wild type (WT). The immobilized W299A, W299 G and WT KsdD respectively maintained 70.5, 65.7 and 38.7 % of their initial activity at the end of 15 reaction cycles. Furthermore, the W299A retained 66.3 % of the initial activity after 30 days of incubation at 4 °C, and was more stable than free KsdD, Thus, the immobilized W299A is a promising biocatalyst for steroid dehydrogenation. In this study, we investigated the application of immobilized enzymes for the dehydrogenation of steroids, which will be of great importance for improving the development of green technology and sustainable use of biocatalysts in the steroid manufacturing industry.

Metabolic Engineering of Isoflavones: An Updated Overview

Isoflavones are ecophysiologically active secondary metabolites derived from the phenylpropanoid pathway. They were mostly found in leguminous plants, especially in the pea family. Isoflavones play a key role in plant-environment interactions and act as phytoalexins also having an array of health benefits to the humans. According to epidemiological studies, a high intake of isoflavones-rich diets linked to a lower risk of hormone-related cancers, osteoporosis, menopausal symptoms, and cardiovascular diseases. These characteristics lead to the significant advancement in the studies on genetic and metabolic engineering of isoflavones in plants. As a result, a number of structural and regulatory genes involved in isoflavone biosynthesis in plants have been identified and characterized. Subsequently, they were engineered in various crop plants for the increased production of isoflavones. Furthermore, with the advent of high-throughput technologies, the regulation of isoflavone biosynthesis gains attention to increase or decrease the level of isoflavones in the crop plants. In the review, we begin with the role of isoflavones in plants, environment, and its benefits in human health. Besides, the main theme is to discuss the updated research progress in metabolic engineering of isoflavones in other plants species and regulation of production of isoflavones in soybeans.

Chalcone Isomerase a Key Enzyme for Anthocyanin Biosynthesis in Ophiorrhiza japonica

Anthocyanins are distributed ubiquitously to terrestrial plants and chalcone isomerase (CHI) catalyzes the stereospecific isomerization of chalcones - a committed step in the anthocyanin biosynthesis pathway. In this study, one gene encoding CHI was isolated from Ophiorrhiza japonica and designated as OjCHI. Multiple sequence alignments and phylogenetic analysis revealed that OjCHI had the conserved CHI active site residues and was classified into type I CHI group. In order to better understand the mechanisms of anthocyanin synthesis in O. japonica, integrative analysis between metabolites and OjCHI expression was conducted. The results showed OjCHI expression matched the accumulation patterns of anthocyanins not only in different tissues but also during the flower developmental stages, suggesting the potential roles of OjCHI in the biosynthesis of anthocyanin. Then biochemical analysis indicated that recombinant OjCHI protein exhibited a typical type I CHI activity which catalyzed the production of naringenin from naringenin chalcone. Moreover, expressing OjCHI in Arabidopsis tt5 mutant restored the anthocyanins and flavonols phenotype of hypocotyl, cotyledon and seed coat, indicating its function as a chalcone isomerase in vivo. In summary, our findings reveal the in vitro as well as in vivo functions of OjCHI and provide a resource to understand the mechanism of anthocyanin biosynthesis in O. japonica.