Re-investigation of in vitro activity of acetohydroxyacid synthase I holoenzyme from Escherichia coli.

Acetohydroxyacid synthase (AHAS) is one of the key enzymes of the biosynthesis of branched-chain amino acids, it is also an effective target for the screening of herbicides and antibiotics. In this study we present a method for preparing Escherichia coli AHAS I holoenzyme (EcAHAS I) with exceptional stability, which provides a solid ground for us to re-investigate the in vitro catalytic properties of the protein. The results show EcAHAS I synthesized in this way exhibits similar function to Bacillus subtilis acetolactate synthase in its catalysis with pyruvate and 2-ketobutyrate (2-KB) as dual-substrate, producing four 2-hydroxy-3-ketoacids including (S)-2-acetolactate, (S)-2-aceto-2-hydroxybutyrate, (S)-2-propionyllactate, and (S)-2-propionyl-2-hydroxybutyrate. Quantification of the reaction indicates that the two substrates almost totally consume, and compound (S)-2-aceto-2- hydroxybutyrate forms in the highest yield among the four major products. Moreover, the protein also condenses two molecules of 2-KB to furnish (S)-2-propionyl-2-hydroxybutyrate. Further exploration manifests that EcAHAS I ligates pyruvate/2-KB and nitrosobenzene to generate two arylhydroxamic acids N-hydroxy-N-phenylacetamide and N-hydroxy-N-phenyl- propionamide. These findings enhance our comprehension of the catalytic characteristics of EcAHAS I. Furthermore, the application of this enzyme as a catalyst in construction of C-N bonds displays promising potential.

Determination of α-Dicarbonyl compounds in traditional Chinese herbal medicines.

α-DCs (α-dicarbonyls) have been proven to be closely related to aging and the onset and development of many chronic diseases. The wide presence of this kind of components in various foods and beverages has been unambiguously determined, but their occurrence in various phytomedicines remains in obscurity. In this study, we established and evaluated an HPLC-UV method and used it to measure the contents of four α-DCs including 3-deoxyglucosone (3-DG), glyoxal (GO), methylglyoxal (MGO), and diacetyl (DA) in 35 Chinese herbs after they have been derivatized with 4-nitro-1,2-phenylenediamine. The results uncover that 3-DG is the major component among the α-DCs, being detectable in all the selected herbs in concentrations ranging from 22.80 µg/g in the seeds of Alpinia katsumadai to 7032.75 µg/g in the fruit of Siraitia grosuenorii. The contents of the other three compounds are much lower than those of 3-DG, with GO being up to 22.65 µg/g, MGO being up to 55.50 µg/g, and DA to 18.75 µg/g, respectively. The data show as well the contents of the total four α-DCs in the herbs are generally in a comparable level to those in various foods, implying that herb medicines may have potential risks on human heath in view of the α-DCs.

[Therapeutic effect of autologous bone marrow stem cell transplantation in the treatment of severe liver damage].

OBJECTIVE: To evaluate the effect of autologous bone marrow stem cell transplantation in the treatment of severe liver damage. METHODS: Autologous bone marrow (50 ml) was harvested from 6 patients aged 44 to 69 years admitted for severe liver damage. Human bone marrow stem cells (HMSCs) were isolated and transplanted in to the patients' liver. At l, 4, 8, and 12 weeks after the transplantation, the changes in ALT, ALB, Cr, TB, PT and the clinical symptoms of the patients were observed. RESULTS: The transplantation of autologous bone marrow stem cells resulted in obvious improvement of the liver function. At 12 weeks after the transplantation, ALT was reduced from 98.4 IU/L to 41.5 IU/L, TB from 136.5 µmol/L to 78.4 µmol/L, Cr from 112.3 µmol/L to 72.1 µmol/L, and ALB rose from 23.3 g/L to 32.6 g/L. The survival of the patients was 100% at 12 weeks, but one patient died at 7 months after the transplantation. The symptoms of the patients were also alleviated after the transplantation. At 12 weeks after transplantation, 3 patients reported improved appetite, 3 showed recovery of physical strength, and 2 showed lessened abdominal swelling. No serious adverse complications in association with the transplantation were found in the in 4 patients available to the follow-up. CONCLUSION: Autologous bone marrow stem cell transplantation can improve the liver function of patients with severe liver damage without causing serious complications.