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Glucose Medium (glucose + medium)
Selected AbstractsCloning and characterization of genes encoding trehalose-6-phosphate synthase (TPS1) and trehalose-6-phosphate phosphatase (TPS2) from Zygosaccharomyces rouxiiFEMS YEAST RESEARCH, Issue 4 2003Hawk-Bin Kwon Abstract In many organisms, trehalose protects against several environmental stresses, such as heat, desiccation, and salt, probably by stabilizing protein structures and lipid membranes. Trehalose synthesis in yeast is mediated by a complex of trehalose-6-phosphate synthase (TPS1) and trehalose-6-phosphate phosphatase (TPS2). In this study, genes encoding TPS1 and TPS2 were isolated from Zygosaccharomyces rouxii (designated ZrTPS1 and ZrTPS2, respectively). They were functionally identified by their complementation of the tps1 and tps2 yeast deletion mutants, which are unable to grow on glucose medium and with heat, respectively. Full-length ZrTPS1 cDNA is composed of 1476 nucleotides encoding a protein of 492 amino acids with a molecular mass of 56 kDa. ZrTPS2 cDNA consists of 2843 nucleotides with an open reading frame of 2700 bp, which encodes a polypeptide of 900 amino acids with a molecular mass of 104 kDa. The amino acid sequence encoded by ZrTPS1 has relatively high homology with TPS1 of Saccharomyces cerevisiae and Schizosaccharomyces pombe, compared with TPS2. Western blot analysis showed that the antibody against S. cerevisiae TPS1 recognizes ZrTPS1. Under normal growth conditions, ZrTPS1 and ZrTPS2 were highly and constitutively expressed, unlike S. cerevisiae TPS1 and TPS2. Salt stress and heat stress reduced the expression of the ZrTPS1 and ZrTPS2 genes, respectively. [source] A member of the YER057c/yjgf/Uk114 family links isoleucine biosynthesis and intact mitochondria maintenance in Saccharomyces cerevisiaeGENES TO CELLS, Issue 6 2001Jong-Myong Kim Background Two paralogs, YIL051c and YER057c, in the Saccharomyces cerevisiae genome are members of the YER057c/Yigf/Uk114 family, which is highly conserved among Eubacteria, Archaea and Eukarya. Although the molecular function of this protein family is not clear, previous studies suggest that it plays a role in the regulation of metabolic pathways and cell differentiation. Results Yil051cp is 70% identical in amino acid sequence to Yer057cp, and differs in that the former is longer by 16 amino acids containing, in part, the mitochondrial targeting signal at the N-terminus of the protein. An HA-tagged protein of Yil051cp is localized strictly in mitochondria, while that of Yer057cp is found in both cytoplasm and nucleus. Disruption of YIL051c (yil051c,) resulted in severe growth retardation in glucose medium due to isoleucine auxotroph, and no growth in glycerol medium due to the loss of mitochondria. An extract prepared from yil051c, cells showed no transaminase activity for isoleucine, while that for valine or leucine was intact. Haploid yil051c, cells newly isolated from the YIL051c/yil051c, hetero-diploids gradually lost mitochondrial DNA within 24 h in the absence of, but not in the presence of, an isoleucine. Mutants either requiring leucine (leu2,112) or isoleucine-valine (bat1,, bat2,) in a YIL051c background showed no changes in mitochondrial DNA maintenance in the absence of requirements. Conclusions Based on these results, we named Yil051c as Ibm1 (Isoleucine Biosynthesis and Mitochondria maintenance1) and concluded that: (i) Ibm1p determines the specificity of isoleucine biosynthesis, probably at the transamination step, (ii) Ibm1p is required for the maintenance of mitochondrial DNA when isoleucine is deficient, and (iii) Isoleucine compensates for the lack of Ibm1p. Taken together, Ibm1p may act as a sensor for isoleucine deficiency as well as a regulator determining the specificity for branched amino acid transaminase. [source] EFFECT OF PHYSICAL FACTORS ON ACETIC ACID PRODUCTION IN BRETTANOMYCES STRAINSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 2 2005C. CASTRO-MARTINEZ ABSTRACT Four species of Brettanomyces (intermedius, bruxellensis, custersianus, clausenii) were examined to ascertain their acetic acid production capacity. The results showed that B. bruxellensis was the strain with the best volumetric productivity ,and ,specific ,production ,rate ,(P = 0.065 gL,1 h,1; ,Vp = 0.43 gg,1h,1). The best kinetic parameters were reached (P = 0.133 gL,1 h,1; Yp/s = 0.23; Pmax = 11.64 gL,1) ,at ,an ,airflow ,of ,288 Lh,1,(0.6 vvm, ,OTR = 124 mgO2L,1,h,1), and substrate inhibition was not observed. The influence of temperature and agitation on acetic acid production by B. bruxellensis in a glucose medium was investigated at different levels, 26, 30, 34C and 250, 350, 450 rpm, respectively. Temperature and agitation were shown to be deci-sive factors (P < 0.05) in acetic acid production at 288 Lh,1(0.6 vvm, OTR = 124 mgO2L,1 h). The optimal conditions for a high volumetric productivity were 30C and 250 rpm, respectively. [source] Effects of glucose and insulin on HepG2-C3A cell metabolismBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2010Vidya V. Iyer Abstract HepG2, hepatocellular carcinoma cells, are used in drug toxicity studies and have also been explored for bioartificial livers. For these applications, the cells are under variable levels of nutrients and hormones, the effects of which on metabolism are poorly understood. In this study, HepG2-C3A cells were cultured under varying levels of glucose (high, low, and glucose-free) and insulin (without and with physiological levels of insulin) for 5 days. Cell growth was found to be comparable between high and low glucose media and lowest for glucose-free medium. Several features of central metabolism were affected profoundly by the medium glucose levels. Glucose consumption was greater for low glucose medium compared to high glucose medium, consistent with known glucose feedback regulation mechanisms. Urea productivity was highest in glucose-free medium. Further, it was seen that lactate acted as an alternative carbon source in the absence of glucose, whereas it acted as a sink for the high and low glucose media. Using a metabolic network flexibility analysis (MNFA) framework with stoichiometric and thermodynamic constraints, intracellular fluxes under varying levels of glucose and insulin were evaluated. The analysis indicates that urea production in HepG2-C3A cells arises via the arginase II pathway rather than from ammonia detoxification. Further, involvement of the putrescine metabolism with glutamine metabolism caused higher urea production in glucose-free medium consistent with higher glutamine uptake. MNFA indicated that in high and low glucose media, glycolysis, glutaminolysis, and oxidative phosphorylation were the main sources of energy (NADH, NADPH, and ATP). In the glucose-free medium, due to very low glycolytic flux, higher malate to pyruvate glutaminolytic flux and TCA cycle contributed more significantly to energy metabolism. The presence of insulin lowered glycerol uptake and corresponding fluxes involved in lipid metabolism for all glucose levels but otherwise exerted negligible effect on metabolism. HepG2-C3A cells thus show distinct differences from primary hepatocytes in terms of energy metabolism and urea production. This knowledge can be used to design media supplements and metabolically engineer cells to restore necessary hepatic functions to HepG2-C3A cells for a range of applications. Biotechnol. Bioeng. 2010;107: 347,356. © 2010 Wiley Periodicals, Inc. [source] | ||||||||||