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PubMed1981

Oxidation of glucosamine by human polymorphonuclear leukocytes.

When exposed to a phagocytic stimulus (opsonized zymosan), human polymorphonuclear leukocytes (PMNs) produced 14CO2 from [1-14C]glucosamine at a rate 10-25% of that produced from glucose under the same conditions. The production of CO2 from glucosamine by intact PMNs was inhibited by glucose and dependent upon activation of the hexosemonophosphate shunt (HMPS). However, the metabolic pathways for the oxidation of glucose and glucosamine by PMNs are not identical. This is suggested by the fact that glucose-6-phosphate dehydrogenase, the initiating enzyme for the HMPS, did not utilize glucosamine-6-phosphate as a substrate. In addition, glucosamine was not oxidized by sonically disrupted PMNs whereas oxidation of glucose by the same preparation was increased sevenfold over intact cells. Taken together, the data suggest that PMNs oxidize glucosamine by converting it to a compound compatible with the enzymes of the HMPS. This conversion requires intact PMNs and/or an as yet unidentified cofactor.

Ascorbic Acid↗
PubMed1979

Tobacco smoke. Effects on pulmonary host defense.

Tobacco smoke affected both the metabolism and function of pulmonary alveolar macrophages (PAM). Phagocytosis of viable Staphylococcus aureus and inert starch particles was minimally but consistently depressed in PAM from rats exposed to tobacco smoke for six months. Oxygen consumption, superoxide and hydrogen peroxide release, and hexose monophosphate shunt activity were elevated in cells from smokers. Oxidation of glucose, labelled in the carbon-six position, remained unchanged. All observed effects of tobacco smoke on oxygen metabolism occurred during phagocytosis and did not affect the basal metabolism of the nonstimulated cell.

Animals↗
PubMed1985

Studies on natural, antibody-dependent, and interleukin-2-activated killer-cell activity of a patient with mucolipidosis III as a test of the mannose-6-phosphate lytic acceptor hypothesis.

The natural (NK), antibody-dependent (K), and interleukin-2-generated (LAK) killer-cell activity of a patient with mucolipidosis III (ML III; an autosomal recessive defect in UDP-N-acetylglucosamine: lysosomal enzyme N-acetylglucosamine-1-phosphotransferase) was studied to determine whether or not the defect in the phosphorylation of lysosomal enzyme mannose residues resulted in a failure of target-cell lysis, as would be predicted from recent studies showing NK inhibition by phosphorylated sugars, especially mannose-6-phosphate. The patient was studied in parallel with normal donors known to be at the high and low extremes of NK activity. The following results were obtained: NK activity was markedly elevated against K562, Molt-4, human fibroblasts, HL-60, and MeWo to levels approximately one to two times that of our previous highest donor and five times the mean of normal donors previously tested. Interleukin-2-generated killer-cell activity and antibody-dependent cell-mediated cytotoxicity against antibody-coated P815 cells were normal and increased, respectively. HNK-1-positive cells were normal in frequency (7.3 +/- 1.7%), while lytic conjugates were proportional to activity (3.9 +/- 0.6 vs 2.7 +/- 0.4% for the "high" donor), and this was attributable to an increased proportion of lytic cells. The addition of fresh serum from the ML III patient had no effect on the NK activity of normal donors and the effects of preincubation with interferon (enhancement), monensin (inhibition), fructose-6-phosphate (inhibition), and mannose-6-phosphate (inhibition) were identical to those seen using lymphocytes from normal donors. Studies on the NK activity of the parents and two normal female siblings showed that the father's NK activity was high, the mother's was low, and both siblings' was intermediate but low. The data obtained suggest that the inability of lymphocytes to phosphorylate lysosomal enzyme mannose residues had no effect on NK-, K-, or LAK-cell function and that the mechanism of target-cell lysis is independent of either a mannose-6-phosphate-bearing lytic moiety or a mannose-6-phosphate-dependent ligand mechanism.

Adult↗
PubMed1984

Decreased labeling of amino acids by inhibition of the utilization of [3H, 14C]glucose via the hexosemonophosphate shunt in rat brain in vivo.

Treatment of rats with 6-aminonicotinamide showed a small but significant decrease in the labeling of amino acids in the brain after injection of [3H]acetate. The results of these experiments also gave evidence of the presence of [3H]glucose and [3H]acetate, and an increase in [3H]glucose content in the brain of 6-aminonicotinamide treated rats. To apportion the contribution of [3H]glucose formed by gluconeogenesis from [3H]acetate to the labeling of amino acids a method was formulated based on the measurement of radioactivity of amino acids, lactate and free sugars in brain after injection of [6-3H]glucose or [1-3H]glucose relative to that after co-injection of [U-14C]glucose or [2-14C]glucose. In contrast to the expected formation of [1,6-3H]glucose by gluconeogenesis from [3H]acetate, 3H-labeled glucose isolated from brain, blood and liver showed the presence of [6-3H]glucose only. The values corrected for the presence of [6-3H]glucose showed that treatment with 6-aminonicotinamide had no effect on the labeling of amino acids by oxidation of [3H]acetate. These findings indicated that a significant decrease in the labeling of amino acids from [U-14C]glucose reported previously and again confirmed using [1-3H], [6-3H], [2-14C] or [U-14C]glucose in the present investigation was not due to the inhibition of the activities of enzymes of the citric acid cycle. These results support the postulated role of the hexosemonophosphate shunt for the utilization of glucose in providing neurotransmitter amino acids glutamate and gamma-aminobutyrate.

Acetates↗
PubMed1982

The effect of inhibition of hexosemonophosphate shunt on the metabolism of glucose and function in rat brain in vivo.

Rats treated 4 hr previously with 6-aminonicotinamide showed a twenty-four fold increase of [14C]phosphogluconate in the adult brain at 30 min after injection of [U-14C]glucose indicating a blockade of the hexosemonophosphate shunt. There was a significant increase in the 14C-content of glucose and glucose-6-phosphate, and a decrease in that of amino acids. [14C]Phosphoglycerate content showed no consistent change after 6-aminonicotinamide treatment. The concentration of glucose and glucose 6-phosphate increased significantly without a significant change in the lactate pool in the brain of 6-aminonicotinamide treated rats. The rate of utilization of glucose in the brain of control rats was 0.73 mumol/min per g of brain. It decreased by 16% in rats treated with 6-aminonicotinamide; the results suggested that both glycolysis and pyruvate oxidation were affected. The amount of glucose utilized in the brain by the hexosemonophosphate shunt was approximately 0.0093 mumol/min per g of brain, i.e. 1.3% of the total rate of utilization of glucose. The observed changes were not due to hypothermia. The rate of glucose utilization was higher in animals exposed to higher ambient temperature and to stress caused by handling. The results were explained by postulating a role for the hexosemonophosphate shunt in providing neurotransmitter amino acids glutamate and gamma-aminobutyrate, and interdependence of brain function and glucose utilization.

6-Aminonicotinamide↗
PubMed1994

Effect of muscle mass on lactate formation during exercise in humans.

To elucidate the mechanisms of lactate formation during submaximal exercise, eight men were studied during one- (1-LE) and two-leg (2-LE) exercise (approximately 11-min cycling) using the catheterization technique and muscle biopsies (quadriceps femoris muscle). The absolute exercise intensity and thus the energy demand for the exercising limb was the same [mean 114 (SEM 7) W] during both 1-LE and 2-LE. At the end of exercise partial pressure of O2 and O2 saturation in femoral venous blood were lower and arterial adrenaline and noradrenaline were higher during 2-LE than during 1-LE. Mean arterial blood lactate concentration increased to 10.8 (SEM 0.8) (2-LE) and 5.2 (SEM 0.4) mmol.l-1 (1-LE) after 10 min of exercise. The intramuscular metabolic response to exercise was attenuated during 1-LE [mean, lactate = 49 (SEM 9); glucose 6-P = 3.3 (SEM 0.3); nicotinamide adenine dinucleotide, reduced = 0.17 (SEM 0.02); adenosine 5'-diphosphate 2.7 (SEM 0.1) mmol.kg dry mass-1] compared to 2-LE [76 (SEM 6); 6.1 (SEM 0.7); 0.21 (SEM 0.02); 3.0 (SEM 0.1) mmol.kg dry mass-1, respectively]. To elucidate whether the lower plasma adrenaline concentration could contribute to the attenuated metabolic response, additional experiments were performed on four of the eight subjects with infusion of adrenaline during 1-LE (1-LEE). Average plasma adrenaline concentration was increased during 1-LEE and reached 2-4 times higher levels than during 2-LE. Post-exercise muscle lactate and glucose 6-P contents were higher during 1-LEE than during 1-LE and were similar to those during 2-LE.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenine Nucleotides↗
PubMed1990

[Mannose-6-phosphate receptors: their role in the transport of lysosomal proteins].

Targetting of newly synthesized lysosomal enzymes to lysosomes requires mannose 6-phosphate receptors. These receptors shuttle between the Golgi apparatus, an organelle of the secretory route, and acidic prelysosomal organelles, which are part of the endocytic route. Vectorial transport of the ligands is ensured by the pH dependence of ligand binding. Ligands are bound at near-neutral pH in the Golgi apparatus and released in the acidic prelysosomal organelles.

Animals↗
PubMed1975

[Glutathione (author's transl)].

Glutathione plays an important role in biology and medicine. Most cells of plants and animals contain high concentrations of reduced glutathione and a much smaller amount of oxidised glutathione. GSH is important for several metabolic functions of live cells, e.g. the protection of oxidative stress by peroxides, mediation of enzyme reactions, regulation of metabolic events, transport of amino acids across cell membranes via the gamma-glutamyl cycle, elimination of foreign compounds by GSH-conjugation, release of neurotransmitter substances. Irreversible perturbations of the glutathione metabolism may be the reason for severe clinical symptoms of hemolytic anemia or, perhaps, of central nervous disease.

Anemia, Hemolytic↗
PubMed1986

Effects of quinolones on granulocyte function in vitro.

Granulocytes (PMN) play an important role in antibacterial host defence. The modulation of PMN-function by different antibiotics has been shown previously. Therefore, we investigated the possible immuno-modulatory effects of four new quinolone antibiotics: ciprofloxacin, norfloxacin, pefloxacin, ofloxacin. Pure PMN-preparations were obtained from healthy volunteers and incubated for 30 min at 37 degrees C with the different quinolones at different concentrations (0.1-1-5-10 mg/l). A complete PMN-functional profile was assayed. At all concentrations tested no significant differences were seen for myeloperoxidase content, superoxide production and chemiluminescence. A significant stimulation of phagocytosis and killing occurred at 10 mg/l of norfloxacin and at 10 mg/l of pefloxacin. An increase of chemotaxis towards formyl-methionyl-leucyl-phenylalanine was noted at 10 mg/l of ofloxacin, while stimulation of hexose monophosphate shunt was seen at 1 mg/l of ciprofloxacin and 10 mg/l of ofloxacin. The mechanism whereby both subinhibitory and inhibitory concentrations of quinolones moderately influence PMN-responsiveness is not yet known. Further studies are needed to elucidate the nature of this quinolone-effect and to assess its relevance in vivo.

Anti-Infective Agents↗
PubMed1977

Enzymatic synthesis of polyprenol monophosphate mannose in insects.

The microsomal fraction of insects was found to contain an enzyme which transfers mannose from guanosine diphosphate mannose to an endogenous or exogenous insect lipid and to other acceptors such as dolichol monophosphate or ficaprenol monophosphate. This activity depended on the presence of Triton X-100 and magnesium ions, the optimal concentration of the latter being 10mM. The optimal temperature of the reaction was 25 degrees C and the maximal activity was obtained at pH 7.9. The mannolipid formed behaved as a monophosphodiester when chromatographed on DEAE-cellulose. Weak acid treatment of the product liberated mannose. Its behaviour both on thin layer and Sephadex G-150 chromatography would indicate the presence of a number of isoprenyl units similar to the dolichol and different from the ficaprenol derivative. Stability to phenol treatment indicated that the lipid fraction of the mannolipid is an alpha-saturated polyprenol phosphate similar to dolichol monophosphate.

Animals↗
PubMed1977

Synthesis of polyprenol-monophosphate- beta -galactose by acetobacter xylinum.

A particulate enzyme preparation from Acetobacter xylinum synthesizes ficaprenol-monophosphate-beta-galactose from ficaprenol monophosphate (FMP) and UDP-galactose in the presence of detergent. The product has the same properties as those previously reported for the compound formed with the endogenous acceptor. Dolichol-monophosphate (DolMP) is also a good galactose acceptor but the product obtained has different properties. Lipid extracts from Acetobacter contain galactose acceptor capacity which is lost by mild acid treatment. FMP behaves in a similar manner but DolMP is resistant to this treatment. It is concluded that the endogeneous acceptor is an allylic phosphate ester of a polyprenol.

Gluconacetobacter xylinus↗