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51.
Diketide N-acetylcysteamine (diketide NAC) thioester precursors were fed to 6-Deoxyerythronolide B synthase (DEBS) ketosynthase-1 inactivated (KS1 degree) Saccharopolyspora erythraea strains to produce 13-substituted erythromycin analogs. This direct feeding process potentially represents a simplified production process over the current analog production system. Titers of these analogs were observed to increase linearly with the diketide concentration up to a precursor-specific saturation level. However, the rate of product formation was lower and the rate of diketide consumption higher with S. erythraea than was previously observed with a recombinant strain of Streptomyces coelicolor. Several strategies were pursued to address the issue of these high diketide consumption rates: (1) elucidation of the locale of diketide degradation, (2) addition of beta-oxidation inhibitors to the cultures, and (3) addition of a sacrificial diketide enantiomer to occupy putative degradative enzymes. Additionally, repeated addition of diketide to an S. erythraea KS1 degrees culture indicated that the titer of these erythromycin analogs is also currently limited by a shorter production period than observed during erythromycin synthesis by the parent strain. These results indicate potential avenues for expanding the use of this precursor-directed system from the generation of limited quantities of erythromycin analogs to a large-scale production system for these compounds. 相似文献
52.
Barroso JB Carreras A Esteban FJ Peinado MA Martínez-Lara E Valderrama R Jiménez A Rodrigo J Lupiáñez JA 《American journal of physiology. Regulatory, integrative and comparative physiology》2000,279(2):R650-R656
We have found conclusive evidence for inducible nitric oxide synthase (iNOS) activity in rainbow trout (Oncorhynchus mykiss) tissue by means of biochemical, immunohistochemical, and immunoblotting analyses. This Ca(2+)-independent enzyme uses L-arginine to produce nitric oxide and L-citrulline. It was significantly inhibited by the L-arginine analogs N(omega)-monomethyl-L-arginine and N(G)-nitro-L-arginine methyl ester. Kinetic analyses showed typical Michaelian behavior with no evidence of cooperative effects. The specific activities of the liver and head kidney enzymes were 27 and 106 pmoles. min(-1). mg protein(-1), respectively, with similar values for K(m) (11 microM), all of which correspond well with the values for other previously characterized iNOS. Western blot analyses revealed a single band of M(R) = 130 kDa tested with an iNOS antiserum. At the ultrastructural level, cells with NADPH-diaphorase activity and iNOS immunoreactivity were identified as being heterophilic granulocytes in head kidney tissue and neutrophils and macrophages in hepatic tissue. The presence of an iNOS isoform in these fish tissues implies that these cells are capable of generating nitric oxide, thus pointing to the potential role of this enzyme in fish defense mechanisms. 相似文献
53.
Tavares E Carreras O Gómez-Tubío A Murillo D Murillo ML 《Journal of physiology and biochemistry》2000,56(3):247-256
This study was designed to examine the effects of supplementation with folic acid and amino acids in dams that consumed ethanol during gestation and lactation to see whether there is an improvement in the intestinal absorption of zinc in pup rats on the 21st day after birth. The rats were randomized into two groups: Ethanol-rats (EG) were administered ethanol during the pregnancy and lactation periods; the ethanol-folic acid group (EFG) received a folic acid and amino acid supplement concomitantly with ethanol administration during pregnancy and lactation. The dams were mated to obtain the first offspring. Two sets of experiments were performed on the offspring at 21 days after birth. In general, in the first set, jejunal zinc absorption in the offspring of EG and EFG groups showed a gradual increase along with increased perfusion time at all assayed concentrations. Jejunal zinc absorption expressed as nmol/intestinal surface was higher in the ethanol-folic acid group than in ethanol animals at all assayed concentrations except at 25 microM concentration. In the second set of experiments, distal ileum zinc absorption in the offspring of ethanolfolic acid dams showed a significant increase at all concentrations tested. These results indicate that supplementation of folic acid and amino acids to dams that consume ethanol during gestation and lactation increase serum and milk zinc levels, although the zinc ingestion is lower. In pups of the supplemented dams, the jejunal and ileal absorption of zinc increased; as a consequence, the serum zinc levels increased. The activity of alcohol dehydrogenase, a metaloenzyme dependent on zinc levels, also increased. 相似文献
54.
A Tauler J Carreras 《Comparative biochemistry and physiology. B, Comparative biochemistry》1987,87(1):117-124
2,3-Bisphosphoglycerate synthase-phosphatase and the hybrid phosphoglycerate mutase/2,3-bisphosphoglycerate synthase-phosphatase have been partially purified from pig brain. Their 2,3-bisphosphoglycerate synthase, 2,3-bisphosphoglycerate phosphatase and phosphoglycerate mutase activities are concurrently lost upon heating and treatment with reagents specific for histidyl, arginyl and lysyl residues. The two enzymes differ in their thermal stability and sensitivity to tetrathionate. Substrates and cofactors protect against inactivation, the protective effects varying with the modifying reagent. The synthase activity of both enzymes shows a nonhyperbolic pattern which fits to a second degree polynomial. The Km, Ki and optimum pH values are similar to those of the 2,3-bisphosphoglycerate synthase-phosphatase from erythrocytes and the hybrid enzyme from skeletal muscle. The synthase activity is inhibited by inorganic phosphate and it is stimulated by glycolyate 2-P. 相似文献
55.
J Carreras J Mezquita G Pons 《Comparative biochemistry and physiology. B, Comparative biochemistry》1982,72(3):401-407
1. The three isozymes of glycerate-2,3-P2 dependent phosphoglycerate mutase present in tissues of mammals and reptiles were inactivated by both treatment with diethylpyrocarbonate and photooxidation with rose bengal. 2. Inactivation of type M isozyme purified from rabbit muscle was complete when two histidine residues per enzyme subunit were carboethoxylated. Hydroxylamine removed the carboethoxy groups, with partial recovery of the enzymatic activity. The cofactor protected the enzyme against inactivation. 3. The inactivation of rabbit muscle phosphoglycerate mutase by photooxidation with methylene blue and rose bengal was sharply pH dependent. The pH profile of enzyme inactivation followed the titration curve of histidine, suggesting that this amino acid was critical for enzyme activity. Glycerate-2,3-P2 did not protect phosphoglycerate mutase against photoinactivation. 相似文献
56.
M Carreras J Carreras F Climent 《Comparative biochemistry and physiology. B, Comparative biochemistry》1988,90(4):739-744
1. Glycerate 1,3-P2-dependent glucose, 1,6-P2 synthase has been purified 2000-fold from pig skeletal muscle, with a yield of 75%. 2. The enzyme possesses fructose 1,6-P2-dependent glucose 1,6-P2 synthase and phosphoglucomutase activities, which represent 0.1 and 60% of the main activity, respectively. 3. Both glucose 1-P and glucose 6-P can act as acceptors of the phosphoryl group from glycerate 1,3-P2. 4. The Km values are 19 microM and 67 nM for glucose 1-P and glycerate 1,3-P2, respectively. 5. The enzyme is inhibited by glycerate 2,3-P2, fructose 1,6-P2, glycerate 3-P, phosphoenolpyruvate and lithium, the inhibition pattern varying with the compound. 相似文献
57.
Damian J. Matuszewski Carolina W?hlby Jordi Carreras Puigvert Ida-Maria Sintorn 《PloS one》2016,11(3)
Image-based screening typically produces quantitative measurements of cell appearance. Large-scale screens involving tens of thousands of images, each containing hundreds of cells described by hundreds of measurements, result in overwhelming amounts of data. Reducing per-cell measurements to the averages across the image(s) for each treatment leads to loss of potentially valuable information on population variability. We present PopulationProfiler—a new software tool that reduces per-cell measurements to population statistics. The software imports measurements from a simple text file, visualizes population distributions in a compact and comprehensive way, and can create gates for subpopulation classes based on control samples. We validate the tool by showing how PopulationProfiler can be used to analyze the effect of drugs that disturb the cell cycle, and compare the results to those obtained with flow cytometry. 相似文献
58.
Joan Ll. Vives-Corrons Josep M. Jou Anna Ester Maria Ibars Josep Carreras Ramon Bartrôns Fernando Climent Santiago Crisolía 《Biochemical and biophysical research communications》1981,103(1):111-117
Incubation of blood with vanadate markedly increases the affinity of hemoglobin for oxygen, decreases the deformability of erythrocytes, reduces their osmotic fragility and alters their morphology, determining the appearance of equinocytic forms. Since vanadate is easily taken up by the erythrocytes and binds hemoglobin, these effects might result from interactions of vanadate with hemoglobin and with membrane proteins at the glycerate-2, 3-P2 and/or ATP binding site. In addition, vanadate inhibits phosphoglycerate mutase, phosphoglucomutase and adenylate-kinase activities from hemolysates, suggesting a possible inhibitory effect on erythrocyte metabolism 相似文献
59.
60.
João Batista A Oliveira Mario Cavagna Claudia G Petersen Ana L Mauri Fabiana C Massaro Liliane FI Silva Ricardo LR Baruffi Jose G Franco Jr 《Reproductive biology and endocrinology : RB&E》2011,9(1):1-7