Transketolase (EC 2.2.1.1, TK) is a thiamine diphosphate-dependent enzyme that catalyzes the transfer of a two-carbon hydroxyacetyl unit with reversible C-C bond cleavage and formation. It is widely used in the production of chemicals, drug precursors, and asymmetric synthesis by cascade enzyme catalysis. In this paper, the activity of transketolase TKTA from Escherichia coli K12 on non-phosphorylated substrates was enhanced through site-directed saturation mutation and combined mutation. On this basis, the synthesis of tartaric semialdehyde was explored. The results showed that the optimal reaction temperature and pH of TKTA_M (R358I/H461S/R520Q) were 32 ℃ and 7.0, respectively. The specific activity on d-glyceraldehyde was (6.57±0.14) U/mg, which was 9.25 times higher than that of the wild type ((0.71±0.02) U/mg). Based on the characterization of TKTA_M, tartaric acid semialdehyde was synthesized with 50 mmol/L 5-keto-d-gluconate and 50 mmol/L non-phosphorylated ethanolaldehyde. The final yield of tartaric acid semialdehyde was 3.71 g with a molar conversion rate of 55.34%. Hence, the results may facilitate the preparation of l-(+)-tartaric acid from biomass, and provide an example for transketolase-catalyzed non-phosphorylated substrates.
Escherichia coli/genetics* ; Transketolase/chemistry* ; Tartrates ; Escherichia coli Proteins/genetics*

AIM:To investigate the reparative effect of extracellular vesicles(EVs)derived from H9 human embryonic stem cells(H9-hESCs)on endometrial injury.METHODS:EVs were isolated from the culture supernatant of H9-hESCs and characterized.A mouse model of endometrial injury was established,with bilateral uterine divisions into an EVs experimental group and a PBS control group.EVs and PBS were injected respectively.Histological changes in the endometrium were assessed using HE staining,and proliferating cell nuclear antigen(PCNA)expression was analyzed via immunohistochemistry.The impact of EVs on the proliferation of human endometrial stromal cells(hEndoSCs)was eva-luated using EdU staining and Western blot.RESULTS:H9-hESCs-EVs exhibited a membrane-structured nanobody with a particle size of(144.7±2.1)nm and expressed characteristic proteins CD63 and TSG101.Compared to the PBS control group,the EVs group showed increased endometrial tissue morphology,thickness,and gland numbers.The average opti-cal density of PCNA expression significantly increased in the EVs group compared to the PBS group(P<0.05).Results from EdU staining and Western blot demonstrated that H9-hESCs-EVs promoted hEndoSC proliferation,with a positive correlation observed between H9-hESCs-EVs and EVs protein concentration(P<0.05).CONCLUSION:H9-hESCs-EVs enhance the repair of endometrial injury by stimulating the proliferation of endometrial stromal cells.

OBJECTIVE: To investigate the effects of compatibility of Gardeniae Fructus and Rhododendri Mollis Flos on the pharmacokinetic behavior of rhodojaponin II and rhodojaponin III of Rhododendri Mollis Flos. METHODS LC-MS/MS of rhodojaponin II and rhodojaponin III in plasma of rats was developed. The method was then applied to study the blood concentrations of rhodojaponin II and rhodojaponin III in rats after oral compatibility administration of Gardeniae Fructus and Rhododendri Mollis Flos and single decoction administration of Rhododendri Mollis Flos, respectively, then their pharmacokinetic parameters were calculated and statistical analysed. RESULTS: The calibration curve was good linearity(r>0.999) in the range of 1-200 ng·mL-1 for rhodojaponin II and 1-100 ng·mL-1 for rhodojaponin III, the precision of quality control samples was less than 12% and the accuracy was less than 20%. After administration of compatibility of Gardeniae Fructus and Rhododendri Mollis Flos and Rhododendri Mollis Flos alone, the AUC0-t of rhodojaponin II in vivo was(260.44±51.67) and (213.39±59.03)h·ng·mL-1, respectively, and the AUC0-t of rhodojaponin III was (60.97±22.78) and (22.38±5.55)h·ng·mL-1, respectively. Compared with single decoction of Rhododendri Mollis Flos administration group, the T1/2 and MRT(0-t)of the rhodojaponin II were significantly increased, the AUC0-t, T1/2, Tmax and CL of the rhodojaponin III were also significantly rised after administration of compatibility of Gardeniae Fructus and Rhododendri Mollis Flos. CONCLUSION After the compatibility of Gardeniae Fructus and Rhododendri Mollis Flos, the rate of absorption and the distribution volume are increased of rhodojaponin III in rats, while the elimination rate has decreased, the T1/2 of rhodojaponin II and rhodojaponin III are extended, but don't affect the absorption rate of rhodojaponin II in rats.

Most of the maxillary impacted third molars are located in the maxillary tuberosity,where the vision and op-eration space are limited.This paper reports a case of surgical extraction of the left maxillary horizontal superhigh impact-ed third molar,which is located between the roots of the adjacent teeth and is closely related to the maxillary sinus.The digital simulation technology was used to reconstruct a three-dimensional visual image of the patient's maxilla,related teeth,and other adjacent anatomical structures to assist in finding the optimal surgical method accurately.Root dis-location before the crown not only protects the roots of the adjacent tooth,but also reduces the risk of maxillary sinus lining damage or perforation during operative procedures,improves the efficiency of the operation,and reduces surgical trauma,which conforms to the concept of minimally inva-sive surgery and provides a new idea and experience for the clinical extraction of such maxillary impacted third molars.