RESUMO
Chalcone isomerase is a key rate-limiting enzyme in the biosynthesis of flavonoids in higher plants, which determines the production of flavonoids in plants. In this study, RNA was extracted from different parts of Isatis indigotica and reverse-transcribed into cDNA. Specific primers with enzyme restriction sites were designed, and a chalcone isomerase gene was cloned from I. indigotica, named IiCHI. IiCHI was 756 bp in length, containing a complete open reading frame and encoding 251 amino acids. Homology analysis showed that IiCHI was closely related to CHI protein of Arabidopsis thaliana and had typical active sites of chalcone isomerase. Phylogenetic tree analysis showed that IiCHI was classified into type Ⅰ CHI clade. Recombinant prokaryotic expression vector pET28a-IiCHI was constructed and purified to obtain IiCHI recombinant protein. In vitro enzymatic analysis showed that the IiCHI protein could convert naringenin chalcone into naringenin, but could not catalyze the production of liquiritigenin by isoliquiritigenin. The results of real-time quantitative polymerase chain reaction(qPCR) showed that the expression level of IiCHI in the aboveground parts was higher than that in the underground parts and the expression level was the highest in the flowers of the aboveground parts, followed by leaves and stems, and no expression was observed in the roots and rhizomes of the underground parts. This study has confirmed the function of chalcone isomerase in I. indigotica and provided references for the biosynthesis of flavonoid components.
Assuntos
Isatis/genética , Proteínas de Plantas/metabolismo , Filogenia , Arabidopsis/genética , Flavonoides , Clonagem MolecularRESUMO
The last essential enzyme in the biosynthetic pathway of trilobatin, phloretin-4'-O glycosyltransferase (P4'-OGT), catalyzes the conversion of trilobatin to phloretin in vitro. However, only a few P4'-OGTs have been found in plants. This study used Malus domestica phloretin-4'-O glycosyltransferase (MdPh-4'-OGT) as a query to identify and clone two UDP-glucuronosyltransferase (UGT) genes, designated UGT74L2 and UGT74L3, from the transcriptome of Andrographis paniculata. According to a phylogenetic tree analysis, UGT74L2 and UGT74L3 belonged to the UGT74 family, which has been linked to several activities in other species. The in vitro enzymatic reaction demonstrated that UGT74L2 could particularly catalyze the formation of trilobatin from phloretin, but UGT74L3 had no effects. By using Ni-NTA affinity chromatography to extract the soluble UGT74L2 recombinant protein, the enzymatic kinetics of the activity was investigated using phloretin as the substrate. The results showed that the optimal temperature and pH for UGT74L2 enzymatic reaction were 40 ℃ and 8.0 (Tris-HCl system), respectively. Three metal ions (Ca2+, Mn2+ and Co2+) showed inhibitory effect on the activity of UGT74L2, while Mg2+ could improve the activity of UGT74L2. Other tested metal ions have no significant effect on UGT74L2. The results of enzymatic kinetic parameters that the Km value was 29.84 μmol·L-1, the kcat was 0.02 s-1, and the kcat·Km-1 was 572.6 mol-1·s-1. By homology modeling, molecular docking and mutation experiments, we found that multiple amino acids residues around the substrate binding pocket play quite an important role during catalytic process, In summary, we identified a novel P4'-OGT gene from medicinal plant Andrographis paniculata and provided a new efficient catalyst to synthesize trilobatin. Meanwhile, this study provides a reference for mining new efficient glycosylation modules from plants.
RESUMO
OBJECTIVE@#To evaluate the effects of a 48-week course of adefovir dipivoxil (ADV) plus Chinese medicine (CM) therapy, namely Tiaogan Jianpi Hexue () and Tiaogan Jiedu Huashi () fomulae, in hepatitis B e antigen (HBeAg)-positive Chinese patients.@*METHODS@#A total of 605 HBeAg-positive Chinese CHB patients were screened and 590 eligible participants were randomly assigned to 2 groups in 1:1 ratio including experimental group (EG, received ADV plus CM) and control group (CG, received ADV plus CM-placebo) for 48 weeks. The major study outcomes were the rates of HBeAg and HBV-DNA loss on week 12, 24, 36, 48, respectively. Secondary endpoints including liver functions (enzymes and bilirubin readings) were evaluated every 4 weeks at the beginning of week 24, 36, and 48. Routine blood, urine, and stool analyses in addition to electrocardiogram and abdominal B scan were monitored as safety evaluations. Adverse events (AEs) were documented.@*RESULTS@#The combination therapy demonstrated superior HBeAg loss at 48 weeks, without additional AEs. The full analysis population was 560 and 280 in each group. In the EG, population achieved HBeAg loss on week 12, 24, 36, and 48 were 25 (8.90%), 34 (12.14%), 52 (18.57%), and 83 (29.64%), respectively; the equivalent numbers in the CG were 20 (7.14%), 41 (14.64%), 54 (19.29%), and 50 (17.86%), respectively. There was a statistically significant difference between these group values on week 48 (P<0.01). No additional AEs were found in EG. Subgroup analysis suggested different outcomes among treatment patterns.@*CONCLUSION@#Combination of CM and ADV therapy demonstrated superior HBeAg clearance compared with ADV monotherapy. The finding indicates that this combination therapy may provide an improved therapeutic effect and safety profile (ChiCTR-TRC-11001263).