Enzymic imbalance in serine metabolism in rat hepatomas.
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ABSTRACT:
SUBMITTER: Snell K
PROVIDER: S-EPMC1153072 | biostudies-other | 1986 Jan
REPOSITORIES: biostudies-other
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Project description:1. Certain enzymes concerned with citrate and glucose metabolism have been measured in two transplanted rat hepatomas, one induced with ethionine (minimal deviation type) and one induced with dimethylaminoazobenzene. In these hepatomas both citrate-cleavage enzyme and NADP-linked isocitrate dehydrogenase in the soluble fraction of the cell were approximately one-third of the values for normal rat liver. These changes have been discussed in relation to the increased citric acid content of tumours and depressed rate of fatty acid synthesis. 2. The glucose-ATP-phosphotransferase activity was below normal liver values in the ethionine-induced tumour but greater than normal in the dimethylaminoazobenzene-induced hepatoma. The apparent K(m) values for the glucose-ATP phosphotransferases of these hepatomas were approx. 8x10(-5)m; no evidence was found for an enzyme with a high K(m) for glucose equivalent to liver glucokinase. 3. Of the enzymes of the pentose phosphate pathway, glucose 6-phosphate-dehydrogenase activity was three to five times as great whereas 6-phosphogluconate-dehydrogenase activity was the same or lower than normal liver in the ethionine-and dimethylaminoazobenzene-induced tumours respectively.
| S-EPMC1264931 | biostudies-other
Project description:1. The enzyme system of rat liver responsible for the degradation of l-serine O-sulphate was purified 300-fold and the optimum conditions for the activity were determined. 2. Inorganic sulphate, pyruvate and ammonia were found to be the products of enzyme action on lserine O-sulphate, being formed in equivalent amounts under all conditions examined. No free l-serine was detected as a product of enzyme action. 3. The enzyme preparation was free from other serine-metabolizing systems such as O-phospho-l-serine phosphatase and l-serine dehydratase. 4. The enzyme has a very narrow substrate specificity and is inactive towards a wide variety of related sulphate esters and amino acids. 5. Pyridoxal 5'-phosphate is capable of catalysing the non-enzymic breakdown of l-serine O-sulphate in the presence of metal salts to yield inorganic sulphate, pyruvate and ammonia as products. 6. The possible role of pyridoxal 5'-phosphate as a coenzyme in the enzymic degradation of l-serine O-sulphate is discussed.
| S-EPMC1198333 | biostudies-other
Project description:The developmental patterns of L-serine hydroxymethyltransferase, L-phosphoserine aminotransferase, L-serine aminotransferase and L-serine dehydratase were determined in rat liver. The results point to an increased capacity for serine biosynthesis de novo in the perinatal period. It is suggested that serine at this time, and also at weaning, may serve as a precursor, via the serine hydroxymethyltransferase reaction, for nucleotide biosynthesis to support the rapid phases of liver growth. The role of the alternative pathways of serine metabolism during neonatal development is discussed.
| S-EPMC1162111 | biostudies-other
Project description:Rationale: Ascorbate is an essential micronutrient known for redox functions at normal physiologic concentrations. In recent decades, pharmacological ascorbate has been found to selectively kill tumour cells. However, the dosing frequency of pharmacologic ascorbate in humans has not yet been defined. Methods: We determined that among five hepatic cell lines, Huh-7 cells were the most sensitive to ascorbate. The effects of high-dose ascorbate on hepatoma were therefore assessed using Huh-7 cells and xenograft tumour mouse model. Results: In Huh-7 cells, ascorbate induced a significant increase in the percentage of cells in the G0/G1 phase, apoptosis and intracellular levels of ROS. High doses of ascorbate (4.0 pmol cell-1), but not low doses of ascorbate (1.0 pmol cell-1), also served as a pro-drug that killed hepatoma cells by altering mitochondrial respiration. Furthermore, in a Huh-7 cell xenograft tumour mouse model, intraperitoneal injection of ascorbate (4.0 g/kg/3 days) but not a lower dose of ascorbate (2.0 g/kg/3 days) significantly inhibited tumour growth. Gene array analysis of HCC tumour tissue from xenograft mice given IP ascorbate (4.0 g/kg/3 days) identified changes in the transcript levels of 192 genes/ncRNAs involved in insulin receptor signalling, metabolism and mitochondrial respiration. Consistent with the array data, gene expression levels of AGER, DGKK, ASB2, TCP10L2, Lnc-ALCAM-3, and Lnc-TGFBR2-1 were increased 2.05-11.35 fold in HCC tumour tissue samples from mice treated with high-dose ascorbate, and IHC staining analysis also verified that AGER/RAGE and DGKK proteins were up-regulated, which implied that AGER/RAGE and DGKK activation might be related to oxidative stress, leading to hepatoma cell death. Conclusions: Our studies identified multiple mechanisms are responsible for the anti-tumour activity of ascorbate and suggest high doses of ascorbate with less frequency will act as a novel therapeutic agent for liver cancer in vivo.
| S-EPMC6857065 | biostudies-literature
Project description:Schizophrenia is a neurodevelopmental disorder featuring chronic, complex neuropsychiatric features. The etiology and pathogenesis of schizophrenia are not fully understood. Oxidative-antioxidant imbalance is a potential determinant of schizophrenia. Oxidative, nitrosative, or sulfuric damage to enzymes of glycolysis and tricarboxylic acid cycle, as well as calcium transport and ATP biosynthesis might cause impaired bioenergetics function in the brain. This could explain the initial symptoms, such as the first psychotic episode and mild cognitive impairment. Another concept of the etiopathogenesis of schizophrenia is associated with impaired glucose metabolism and insulin resistance with the activation of the mTOR mitochondrial pathway, which may contribute to impaired neuronal development. Consequently, cognitive processes requiring ATP are compromised and dysfunctions in synaptic transmission lead to neuronal death, preceding changes in key brain areas. This review summarizes the role and mutual interactions of oxidative damage and impaired glucose metabolism as key factors affecting metabolic complications in schizophrenia. These observations may be a premise for novel potential therapeutic targets that will delay not only the onset of first symptoms but also the progression of schizophrenia and its complications.
| S-EPMC7175146 | biostudies-literature
Project description:Serine is a substrate for nucleotide, NADPH, and glutathione (GSH) synthesis. Previous studies in cancer cells and lymphocytes have shown that serine-dependent one-carbon units are necessary for nucleotide production to support proliferation. Presently, it is unknown whether serine metabolism impacts the function of non-proliferative cells, such as inflammatory macrophages. We find that in macrophages, serine is required for optimal lipopolysaccharide (LPS) induction of IL-1β mRNA expression, but not inflammasome activation. The mechanism involves a requirement for glycine, which is made from serine, to support macrophage GSH synthesis. Cell-permeable GSH, but not the one-carbon donor formate, rescues IL-1β mRNA expression. Pharmacological inhibition of de novo serine synthesis in vivo decreased LPS induction of IL-1β levels and improved survival in an LPS-driven model of sepsis in mice. Our study reveals that serine metabolism is necessary for GSH synthesis to support IL-1β cytokine production.
| S-EPMC6447453 | biostudies-literature
Project description:Serine is a substrate for nucleotides, NADPH and glutathione (GSH) synthesis. Previous studies in cancer cells and lymphocytes have shown that serine-dependent one-carbon units are necessary for nucleotide production to support proliferation. Presently, it is unknown whether serine metabolism impacts the function of non-proliferative cells, such as inflammatory macrophages. We find that in macrophages, serine is required for optimal lipopolysaccharide (LPS) induction of IL-1β mRNA expression, but not inflammasome activation. The mechanism involves a requirement for glycine, which is made from serine, to support macrophage glutathione (GSH) synthesis. Cell-permeable GSH, but not the one-carbon donor formate, rescues IL-1β mRNA expression. Pharmacological inhibition of de novo serine synthesis in vivo decreased LPS induction of IL-1β levels and improved survival in an LPS-driven model of sepsis in mice. Our study reveals that serine metabolism is necessary for GSH synthesis to support IL-1β cytokine production.
2019-01-15 | GSE125036 | GEO
Project description:Routes for cysteine biosynthesis are still unknown in many archaea. Here we find that the hyperthermophilic archaeon Thermococcus kodakarensis generates cysteine from serine via O-phosphoserine, in addition to the classical route from 3-phosphoglycerate. The protein responsible for serine phosphorylation is encoded by TK0378, annotated as a chromosome partitioning protein ParB. The TK0378 protein utilizes ADP as the phosphate donor, but in contrast to previously reported ADP-dependent kinases, recognizes a non-sugar substrate. Activity is specific towards free serine, and not observed with threonine, homoserine and serine residues within a peptide. Genetic analyses suggest that TK0378 is involved in serine assimilation and clearly responsible for cysteine biosynthesis from serine. TK0378 homologs, present in Thermococcales and Desulfurococcales, are most likely not ParB proteins and constitute a group of kinases involved in serine utilization.
| S-EPMC5120207 | biostudies-literature
Project description:BACKGROUND:Therapies targeting altered activity of pyruvate dehydrogenase (PDH) and pyruvate carboxylase (PC) have been proposed for hepatomas. However, the activities of these pathways in hepatomas in vivo have not been distinguished. Here we examined pyruvate entry into the tricarboxylic acid (TCA) cycle through PDH versus PC in vivo using hepatoma-bearing rats. METHODS:Hepatoma-bearing rats were generated by intrahepatic injection of H4IIE cells. Metabolism of 13C-labeled glycerol, a physiological substrate for both gluconeogenesis and energy production, was measured with 13C NMR analysis. The concentration of key metabolites and the expression of relevant enzymes were measured in hepatoma, surrounding liver, and normal liver. RESULTS:In orthotopic hepatomas, pyruvate entry into the TCA cycle occurred exclusively through PDH and the excess PDH activity compared to normal liver was attributed to downregulated pyruvate dehydrogenase kinase (PDK) 2/4. However, pyruvate carboxylation via PC and gluconeogenesis were minimal, which was linked to downregulated forkhead box O1 (FoxO1) by Akt activity. In contrast to many studies of cancer metabolism, lactate production in hepatomas was not increased which corresponded to reduced expression of lactate dehydrogenase. The production of serine and glycine in hepatomas was enhanced, but glycine decarboxylase was downregulated. CONCLUSIONS:The combination of [U-13C3]glycerol and NMR analysis enabled investigation of multiple biochemical processes in hepatomas and surrounding liver. We demonstrated active PDH and other related metabolic alterations in orthotopic hepatomas that differed substantially not only from the host organ but also from many earlier studies with cancer cells.
| S-EPMC6892165 | biostudies-literature
Project description:Staphylococcus saprophyticus is the only species of Staphylococcus that is typically uropathogenic and possesses a gene coding for a D-serine-deaminase (DsdA). As D-serine is prevalent in urine and toxic or bacteriostatic to many bacteria, it is not surprising that the D-serine-deaminase gene is found in the genome of uropathogens. It has been suggested that D-serine-deaminase or the ability to respond to or to metabolize D-serine is important for virulence. For uropathogenic Escherichia coli (UPEC), a high intracellular D-serine concentration affects expression of virulence factors. S. saprophyticus is able to grow in the presence of high D-serine concentrations; however, its D-serine metabolism has not been described. The activity of the D-serine-deaminase was verified by analyzing the formation of pyruvate from D-serine in different strains with and without D-serine-deaminase. Cocultivation experiments were performed to show that D-serine-deaminase confers a growth advantage to S. saprophyticus in the presence of D-serine. Furthermore, in vivo coinfection experiments showed a disadvantage for the ΔdsdA mutant during urinary tract infection. Expression analysis of known virulence factors by reverse transcription-quantitative PCR (RT-qPCR) showed that the surface-associated lipase Ssp is upregulated in the presence of D-serine. In addition, we show that S. saprophyticus is able to use D-serine as the sole carbon source, but interestingly, D-serine had a negative effect on growth when glucose was also present. Taken together, D-serine metabolism is associated with virulence in S. saprophyticus, as at least one known virulence factor is upregulated in the presence of D-serine and a ΔdsdA mutant was attenuated in virulence murine model of urinary tract infection.
| S-EPMC3837983 | biostudies-literature