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PubMed1979

Control of membrane lipid synthesis in Escherichia coli during growth and during the stringent response.

The regulation of phospholipid synthesis in cells of Escherichia coli was studied in vivo during growth and during the stringent response to amino acid starvation. Strains harboring the hybrid plasmid pLC44-14 (Clark, L., and Carbon, J. (1976) Cell 9, 91-99), which had increased levels of glycerophosphate acyltransferase, were used to study the involvement of this enzyme in the control of phospholipid synthesis. In addition, regulation was studied by measuring the levels of three early intermediates of phospholipid synthesis:phosphatidic acid, CDP-diglyceride, and dCDP-diglyceride. The liponucleotides were measured by a new enzymatic method which allows determinations to be made on crude lipid extracts. Results from experiments on growing cells are consistent with regulation of membrane lipid synthesis occurring in fatty acid synthesis or at the level of glycerophosphate acylation, but not at any later step. Experiments on the inhibition of lipid synthesis during the stringent response make it possible to rule out explanations which involve the inhibition of a single enzyme; enzymes both before and after the liponucleotides in phospholipid synthesis must be affected.

Amino Acids↗

PubMed1975

A transport system for phosphoenolpyruvate, 2-phosphoglycerate, and 3-phosphoglycerate in Salmonella typhimurium.

Salmonella typhimurium strain LT-2 was found to utilize phosphoenolpyruvate, 2-phosphoglycerate, and 3-phosphoglycerate as sole sources of carbon and energy for growth, but Escherichia coli strains did not. The following evidence suggests that this growth difference was due to the presence in Salmonella cells of an inducible phosphoglycerate permease distinct from previously studied transport systems: (a) The ability of cells to take up 3-phospho[14-C]glycerate was induced by growth in the presence of phosphoenolpyruvate, 2-phosphoglycerate, or 3-phosphoglycerate, but not glycerate, alpha-glycerophosphate, or other carbon sources tested. (b) Uptake of 3-phospho[14-C]glycerate was strongly inhibited by the three nonradioactive inducers of 3-phosphoglycerate uptake, but not by glycerate or alpha-glycerophosphate. (c) Mutants which lost the ability to utilize and take up 3-phosphoglycerate simultaneously lost the ability to utilize 2-phosphoglycerate and phosphoenolpyruvate, but not other compounds tested. (d) Mutant strains which constitutively synthesized the phosphoglycerate transport system could use both phosphoglycerates and phosphoenolpyruvate as sole sources of phosphate at low substrate concentrations. (e) A strain lacking alkaline and acid phosphatases could still grow with 3-phosphoglycerate as sole carbon source. Maximal rates of 3-phospho[14-C]glycerate uptake occurred at pH 6 in the presence of an exogenous energy source. The apparent Km for 3-phosphoglycerate uptake under these conditions was about 10-minus 4 M. The maximal uptake rate (but not the Km) was dependent on potassium ions. Although synthesis of the phosphoglycerate transport system appeared to be under adenosine 3:5-monophosphate control, glucose repressed induction only slightly. The genes controlling synthesis of the phosphoglycerate transport system (pgt genes) appeared to map at about 74 min on the Salmonella chromosome.

Biological Transport↗

PubMedDate not supplied

Adipogenic activity in the plasma of genetically obese Zucker rats.

The potential of plasma to stimulate differentiation and lipid filling of adipose precursors in primary culture was investigated in the groups of genetically obese Zucker rats (fafa) and their lean littermates (FaFa). The effect of age, feeding status and possible role of growth hormone in the process of adipogenesis was also studied. Differences in lipid-filling activity of the tested plasma samples were much more dependent on age than the genotype of plasma donors were. The plasma taken from the oldest (20-week-old) rats stimulated the accumulation of triglycerides in the cells to significantly higher levels than the plasma from other rats. The influence of the feeding status on the lipid-filling activity of plasma was not significant. The differentiation potential of plasma in terms of the stimulation of glycerophosphate dehydrogenase activity measured in adipocyte precursors was 30-50% higher when the culture medium contained plasma from obese rats. Furthermore, glycerophosphate dehydrogenase activity in the growing cells declined with age and tended to be higher in the presence of plasma from fed rats. It was the growth hormone that was in a considerable degree responsible for the differentiation potential of Zucker rat plasma. This effect of growth hormone seemed to be less dependent on fafa genotype. It is, therefore, suggested that in addition to growth hormone, other factors in the plasma of genetically obese Zucker rats might be important in the development of obesity in this rat strain.

Adipose Tissue↗

PubMedDate not supplied

[Effect of adrenocorticotropic hormone on the biosynthesis of glycerolipid components in the rat liver].

Single administration of ACTH led to stimulation of synthesis of saturated and monoenic fatty acids in liver tissue as well as to their esterification with formation of triacyl glycerols. The hormone inhibited elongation and desaturation of fatty acids and decreased the formation of polyenic fatty acids in liver tissue. Cycloheximide alone or simultaneously with ACTH activated synthesis of unsaturated and monoenic fatty acids and stimulated the glycerophosphate shunt of triacyl glycerols synthesis. The tropic hormone activated glyceroneogenesis contributing to an increase in concentration of both alpha-glycerophosphate and long-chain fatty acids in hepatocytes; either ACTH or cycloheximide stimulated the triacyl glycerols synthesis via induction of the key enzymes by excess of the substrates. Consumption of acetyl-CoA, derived from labeled leucine, for biosynthesis of individual lipids was regulated by other mechanisms distinct from those involved in consumption of acetyl-CoA pool, derived from labelled acetate.

Adrenocorticotropic Hormone↗

PubMed1977

A sensitive radioenzymatic assay for glycerol and acylglycerols.

A sensitive radioenzymatic assay for glycerol and acylglycerols is described. The assay depends on the quantitative phosphorylation of glycerol to glycerophosphate by glycerol kinase using [gamma-32P]ATP as a substrate. The 32P content of the formed glycerophosphate is determined and gives a measure of the original glycerol content. Acylglycerols can be determined by prior hydrolysis to glycerol. The assay is sensitive to about 0.1 nmol of glycerol and can be extended to 100 nmol. The assay can be applied to the determination of acylglycerols separated by thin-layer chromatography in amounts as low as 0.5 nmol. The assay is particularly useful in the determination of the specific activity of 14C- or 3H-labeled glycerol moeities.

Animals↗

PubMed1977

Enzymic markers of thyroid C cells in some rodents.

The paper provides comparative data of the localization of histochemical reactions demonstrating the activities of alpha-glycerophosphate and succinate dehydrogenases, acid phosphatase, non-specific esterases and non-specific acetylcholinesterase in the C cells of thyroids of 26 animals belonging to 5 rodent species. The family Muridae is represented by the Wistar albino rat and albino mouse, the family Microtidae by the bank vole Clethrionomys glareolus (Schreber 1780), the field vole Microtus agrestis L. 1761, and the pine vole Pitymys subterraneus De Selys-Longchamps 1825. The observed enzyme activity differences were most conspicuous on comparing the rat and mouse thyroids and in a much less degree the Microtidae thyroids. Among the histochemical reactions tested that for succinate dehydrogenase proved to be least effective as a C cell marker, alpha-glycerophosphate dehydrogenase being better, and acid phosphatase and non-specific esterases the best (not in the rat thyroid). The reaction for non-specific cholinesterase (with some limitations) gave satisfactory results in the C cells of all animal's thyroids. The present paper continues earlier studies [19] on the morphology of the C cells in thyroid glands of the rodents of the families Muridae and Microtidae and aims at supplementing them with histochemical data of enzymic activities. It deals with enzyme reactions that are employed as C cell markers in Mammals other than Rodents.

Acetylcholinesterase↗

PubMed1987

Relation of lung fatty acid binding protein to the biosynthesis of pulmonary phosphatidic acid and phosphatidylcholine.

The activities of glycerophosphate and lysophosphatidylcholine (LPC) acyltransferases were determined using lung microsomes in the presence of lung fatty acid binding protein (FABP). The synthesis of phosphatidic acid (PA) was increased two- to fourfold in the presence of FABP as compared to albumin. Lung FABP did not increase the incorporation of palmitoyl CoA into phosphatidylcholine. The results indicate that FABP-bound fatty acyl CoA may be a preferred substrate for glycerophosphate acyltransferase.

1-Acylglycerophosphocholine O-Acyltransferase↗

PubMed1986

[Development of esterification capacity of fatty acids in the adipocytes of the rat before weaning: the effect of milk overfeeding].

During the suckling period, lipid storage in rat adipose tissue arises from exogenous triglycerides, as milk contains a large amount of lipid. In the present work, we studied the effect of overfeeding during the suckling period on the developmental pattern of the fatty acid esterification pathway in fat cells. Early overfeeding was induced by restricting litter size; at 2 days of age, the pups were randomly distributed to form litters of 4 (overfed group) or 8 (controls). During the suckling period the activity of lipoprotein lipase (LPL), glycerophosphate dehydrogenase (G3PDH), glycerophosphate acyl transferase (GPAT) and acyl CoA ligase were measured in isolated fat cells from the inguinal adipose tissue. As early as 10 days of age, plasma triglyceride levels were increased in overfed pups as compared to the controls and, in these animals, the adipose tissue was overdeveloped, mainly due to fat cell hypertrophy. At that age, overfeeding induced a significant increase in LPL and GPAT activities, but acyl CoA ligase and GPDH were not modified in overfed pups. Fat cell hypertrophy appeared to be responsible for the increased GPAT activity in the overfed pups. On the contrary, the effect of overfeeding on LPL activity was not only related to fat cell enlargement, as the enzyme activity continued to increase in the overfed rats when expressed per unit of cell surface area. These results show that overfeeding during the suckling period rapidly induced an increase in the fat storage capacity of the adipose tissue. This suggests that circulating triglyceride levels could regulate directly or through hormonal control the activity of the fatty acid esterification pathway in fat cells.

Adipose Tissue↗

PubMed1986

[Enzymatic coordination indices of leukocytes in the prognosis of mouse resistance to staphylococcal toxin].

The activity of succinate, lactate and alpha-glycerophosphate dehydrogenases, as well as acid phosphatase, in the lymphocytes and neutrophils of the blood was studied in noninbred white mice prior to the intraperitoneal injection of 1 LD50 of staphylococcal toxin. As the result of intoxication, a half of the animals died and the other half survived. The two groups of the animals differed in the levels of the activity of succinate dehydrogenase and hyaloplasmatic alpha-glycerophosphate dehydrogenase in the neutrophils and lymphocytes, and also differed in the stability of correlations between the activity of succinate and lactate dehydrogenases in the lymphocytes and neutrophils and, besides, between the activity of lactate dehydrogenase in these types of cells.

Animals↗

PubMed1985

Absence of alkaline phosphatase-linked inorganic phosphate transport in the chick jejunum.

The role of non-specific alkaline phosphatase-linked inorganic phosphate (Pi) transport in the chick jejunum was investigated by using the everted gut sac technique. The highest intensity of transport was observed for free Pi. The maximal transport rate was considerably reduced when beta-glycerophosphate was used as a single source of phosphorus. These results suggested absence of the alkaline phosphatase-linked transport system for inorganic phosphate in the epithelium of the chick jejunum. Studies of Mg effect on Pi absorption as well as examination of temporal changes in Pi transport rate and beta-glycerophosphate hydrolysis rate by intestinal brush border alkaline phosphatase gave further backing to this suggestion.

Alkaline Phosphatase↗

PubMed1985

[Tryptophan of facultative methylotrophic bacteria Pseudomonas sp. M. II. Regulation of tryptophan biosynthesis].

Regulation of tryptophan biosynthesis of facultative methylotrophic Pseudomonas sp. M was studied. Repression of the trpE, trpD and trpC genes by tryptophan was demonstrated. It was also shown that the trpE and trpDC genes are derepressed noncoordinately. No regulation of the trpF gene product could be demonstrated, indicating that its synthesis is constitutive. The trpA and trpB genes are inducible by indol-3-glycerophosphate. Anthranilate synthase and tryptophan synthase were sensitive to the feedback inhibition. The tryptophan concentrations giving 50% inhibition were estimated to be 9 microM and 1 microM, respectively. Experimental evidence for activation of the N-5-phosphoribosyl anthranilate isomerase and for inhibition of the indol-3-glycerophosphate synthase by some tryptophan intermediates was obtained.

Anthranilate Synthase↗

PubMed1972

A histoenzymatic study of human intracranial atherosclerosis.

A light microscopy study on the localization of enzyme activity within atherosclerotic human intracranial arteries was performed on autopsy material obtained within 4 hours of death. The data suggests that the atherosclerotic process first goes through a proliferative phase and then a degenerative phase culminating in the formation of a plaque. In the proliferative phase, smooth muscle cell proliferation has formed a thickened intima. Tetrazolium reductase, adenosine triphosphatase (ATPase) and adenosine monophosphatase (AMPase) activities are present in these cells, while all dehydrogenases and acid phosphatase activities were weak or not present. As the degenerative phase commences, an area of necrosis, lipid and macrophage accumulation is formed on the lumen side of the elastica. This area increases in size until a plaque is formed. Unsaturated polar and nonpolar lipid, cholesterol, alpha-glycerophosphate dehydrogenase, acid phosphatase, and AMPase activities are associated with these areas and in foam cells, which are often found in the thickened intima of the proliferative phase. Tetrazolium reductase and ATPase activities decrease in the thickened intima as the area of necrosis increases in size, while dehydrogenase activity, except that for alpha-glycerophosphate, remains low or not present. Patterns of enzyme alterations for various stages of the disease process in intracranial arteries, the aorta and coronary arteries suggest a similar, if not identical, progression of the atherosclerotic process, irrespective of known differences in the prevalence of atherosclerosis.

Acid Phosphatase↗

PubMed1972

Characterization of glycerophosphorylcholine, -ethanolamine, -serine, -inositol, and -glycerol hydrolytic activity in housefly larvae.

Homogenates of Musca domestica (housefly) larvae contain glycerophosphodiesterase activity, which is found in the supernatant fluid after centrifugation at 88,000 g. The phosphodiesterase is inhibited by EDTA and is stimulated by Mg(2+), Ni(2+), Co(2+), and Mn(2+). The pH optimum is 7.2. The enzyme is stable to heating at 50 degrees C for 15 min and is insensitive to sulfhydryl inhibitors. Glycerophosphoryl diesters of choline, ethanolamine, inositol, serine, glycerol, and beta-methylcholine are hydrolyzed to the common product, l-alpha-glycerophosphate, and the appropriate free alcohol. The rate of glycerophosphorylcholine hydrolysis is 70% greater than the rate of hydrolysis of the other glycerophosphodiesters. Apparent K(m) values for glycerophosphorylcholine, glycerophosphorylethanolamine, and glycerophosphoryl-beta-methylcholine are 2-4 x 10(-4) m, and for glycerophosphorylinositol, 2 x 10(-3) m. Competitive studies using various pairs of substrates, as well as the exchange of free choline into both glycerophosphorylcholine and glycerophosphorylinositol, suggest that a single enzyme cleaves all substrates. Product inhibition and reversal of the reaction were not detected. Choline, but not l-alpha-glycerophosphate, exchanges into glycerophosphorylcholine and glycerophosphorylinositol.

Ammonium Sulfate↗

PubMed1979

[Effect of proteolysis inhibitors on the phagocytic activity and the cytoplasmic enzymatic activity in the leukocytes of white mice].

The injection of proteolytic inhibitors changes phagocytosis and metabolism of leucocytes in different ways. The polyvalent inhibitor, inhitril, increased phagocytosis but does not change digestive activity of leucocytes. Activities of acid phosphatase, peroxidases and succinatedehydrogenase as well as glycogen contents are seen decreased, whereas activity of glycerophosphate dehydrogenase increases, and that of lactate dehydrogenase does not change. Anti-tryptic serum decreases phagocytosis, both digestive and enzymatic activities of leucocytes, glycogen accumulation being observed. Anti-kallikrein serum decreases phagocytosis and activity of lactate dehydrogenase, and does not change glycogen accumulation and activities of digestion and of acid phosphatase. In addition, activities of succinate-, glycerophosphate dehydrogenase and peroxidase increase.

Animals↗

PubMed1979

[Nonspecific esterase and alpha-glycerolphosphate dehydrogenase activity and the fat content in the regenerating chicken liver].

The data on histochemical study of changes in the activity of esterases, alpha-glycerophosphate dehydrogenase and the fat content in the chick regenerating liver are presented. The accumulation of the fat in hepatocytes during the early periods of regeneration (1--5th day of the experiment) is partially conditioned by the reduction of the activity of nonspecific esterases. The maximal liver steatosis is accompanied also by an increase in the activity of alpha-glycerophosphate dehydrogenase which indicates intensification of glycolysis and synthesis of triacylglycerines (liver spare lipids) during regeneration.

Animals↗

PubMedDate not supplied

[Effect of alpha-tocopherol on the enzymatic activity of phospholipid biosynthesis and breakdown in burn injury].

Burns affected the content of L-alpha-glycerophosphate /L-alpha-GP/ in rats; its level was reduced within 15 days after burns. Phasic changes in L-alpha-glycerophosphate dehydrogenase and glycerokinase activities in liver and brain tissues and phospholipase A in blood were also observed. Intraperitoneal administration of alpha-tocopheryl acetate into rats subjected to burns abolished the decrease in content of L-alpha-GP although the activity of the drug varied within this 15 day period. In brain the activity of these enzymes was increased 2-3-fold. The data obtained are in good agreement with those published previously and indicating loss of phospholipids in liver and brain tissus following burns.

Animals↗

PubMed1979

[Histo- and cytochemical enzymatic characteristics of breast cancer].

In most of the cases studied, histo- and cytoenzymochemical values of metabolism in cancer of the mammary gland correlate with the histological type, differentiation level and the degree of the tumor malignancy. As the histological degree of malignancy increases and the level of differentiation of the mammary cancer decreases, the activity of glycolysis and pentous shunt enzymes, lactate dehydrogenase and glucose-6-phosphate dehydrogenase, increases and that of the Krebs cycle enzymes, succinate and malate dehydrogenase, as well as the enzyme of glycerophosphate shuttle mechanism and oxidation of glycerol-L-glycerophosphate dehydrogenase decreases simultaneously. These data suggest that histo- and cytochemical methods of the enzyme activity determinations may be used for the specification of the prognosis and choosing of the auxiliary methods for the therapy of the mammary gland cancer based both on morphology and metabolism of the tumour.

Adult↗

PubMed1968

Lipogenesis in human adipose tissue.

The pathways and some critical enzymes involved in lipogenesis in adipose tissue from 82 patients have been studied. Of the glucose-(14)C metabolized to lipid by isolated adipose cells, approximately 0.6% was recovered in fatty acids and the rest in glyceride-glycerol. Palmitate-1-(14)C was readily incorporated into neutral lipid. Homogenates of human adipose tissue contained an active alpha-glycerophosphate dehydrogenase which was approximately twice as active as malate dehydrogenase. Mitochondria of human adipose tissue contained an NAD-independent alpha-glycerophosphate dehydrogenase; the reaction product, di-hydroxyacetone phosphate, was recovered extramitochondrially. Homogenates of human adipose tissue also contained an active fatty acyl CoA synthetase which required ATP, CoA, and Mg(++) for maximal activity. The activity of acyl CoA synthetase varied greatly in a group of 40 patients. By contrast, the range of activity of malate dehydrogenase assayed in the same group of patients was much smaller. When palmitate or palmitoyl CoA was used as substrate, no difference was found in the rate of incorporation of alpha-glycerol-1,3-(14)C phosphate into neutral lipid. If time was allowed for activation of palmitate, the incorporation of alpha-glycerol-1,3-(14)C phosphate into lipid was 3.5 times greater than for unactivated palmitate. Palmitate (200 mM) stimulated lipogenesis in homogenates of human adipose tissue and then caused a severe inhibition at 700 mM. Arachidate over the same concentration range did not depress lipogenesis below initial values.

Adenosine Triphosphate↗