Authors:Ashraf El-Sayed, Salwa Khalaf, Gamal Abdel-Hamid, and Mohamed El-Batrik
The potency for production of cystathionine γ-lyase (CGL) by the fungal isolates was screened. Among the tested twenty-two isolates, Aspergillus carneus was the potent CGL producer (6.29 U/mg), followed by A. ochraceous (6.03 U/mg), A. versicolor (2.51 U/mg), A. candidus (2.12 U/mg), A. niveus and Penicillium notatum (2.0 U/mg). The potent six isolates producing CGL was characterized morphologically, A. carneus KF723837 was further molecularly characterized based on the sequence of 18S–28S rDNA. Upon sulfur starvation, the yield of A. carneus extracellular CGL was increased by about 1.7- and 4.1-fold comparing to non-sulfur starved and L-methionine free medium, respectively. Also, the uptake of L-methionine was duplicated upon sulfur starvation, assuming the activation of specific transporters for L-methionine and efflux of CGL. Also, the intracellular thiols and GDH activity of A. carneus was strongly increased by S starvation, revealing the activation of in vivo metabolic antioxidant systems. Upon irradiation of A. carneus by 2.0 kGy of γ-rays, the activity of CGL was increased by two-fold, regarding to control, with an obvious decreases on its yield upon further doses. Practically, CGL activity from the solid A. carneus cultures, using rice bran as substrate, was increased by 1.2-fold, comparing to submerged cultures, under optimum conditions.
Authors:A. E. Mekonnen, Radha Prasanna, and B. D. Kaushik
, P. (1975) Effect of L-methionine-DL-sulphoximine on the assimilation of newly fixed NH 3 , acetylene reduction and heterocyst formation in Anabaena cylindrica. Biochem. Biophys. Res. Commun. 65 , 846-856.
Effect of L-methionine
Authors:Lj. Glavaš-Obrovac, T. Klapec, I. Karner, and M. L. Mandić
Studies performed so far on different human carcinoma cell lines, as well as numerous case-control and epidemiological studies have given proof to the protective effects of selenium against cancer. However, the anticancer properties of selenium are site-specific. The aim of this work was to evaluate the cytotoxic effect of selenium against CaCo2 human colon carcinoma cells, and SW620 lymph node metastasis of colon carcinoma cell line. Three selenium compounds, seleno-DL-cystine (SeC), seleno-L-methionine (SeM) and sodium selenite were used. Initial number of cells was 210 4 and the cells were incubated for 72 h with the aforementioned Se compounds at 10, 100 and 1000 µmol Se concentrations. Cytotoxicity was measured by the MTT cell survival assay. In the present study, decreased viabilities of both CaCo2 and SW620 cells were established following the treatment with selenite, SeC, and SeM. At 10 µmol Se levels all three chemical forms exerted a more or less anticipated cytotoxic effect with viability decreases ranging from 22 to 37%. However, the other two levels of 100 and 1000 µmol Se did not exhibit an expected proportional rise in cytotoxic effect compared to 10 µmol, which warrants further research on the reasons for increased resistance of these cells. Cell morphology also indicates that investigated Se forms induced apoptotic cell death in both cell lines. The results confirm the applicability of Se in the prevention and treatment of the investigated cancer sites.
Authors:S. Hussein, É. Gelencsér, M. Polgár, and György Hajós
Buffalo and cow milk caseins were submitted to hydrolysis either with á -chymotrypsin or with pepsin. Enzymatic peptide modification (EPM) was carried out by using L-methionine ethyl ester in the reaction mixture. As catalyst, á -chymotrypsin or pepsin was used. The incorporation of methionine in to the peptide chains in the presence of á -chymotrypsin showed an optimum value at 0.14 g Met added to the reaction mixture/1 g hydrolysate in both cases. In the case of pepsin used as catalyst, the optimal Met-enrichment was at 0.14 g Met added to the reaction mixture/1 g buffalo casein hydrolysate and at 0.34 g Met/1 g cow casein hydrolysate. The covalent nature of the amino acid incorporation was confirmed by SDS - polyacryl amide gel electrophoresis in the presence of urea. Electrophoretic patterns of the products indicate that transpeptidation plays an essential role in the EPM reaction. Antigenic character of the EPM- products was investigated in vitro by competitive indirect ELISA. Enzymatic peptide modification with methionine enrichment seems to be an efficient method for the reduction of the antigenic/potential allergenic character and for the improvement of the nutritive value of buffalo and cow milk caseins.