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PubMed1980

Lactose and D-galactose metabolism in Staphylococcus aureus. III. Purification and properties of D-tagatose-6-phosphate kinase.

D-Tagatose-6-phosphate kinase, an inducible enzyme that functions in the metabolism of lactose and D-galactose in Staphylococcus aureus, was purified about 300-fold from an extract of D-galactose-grown cells. The enzyme catalyzed the nucleoside triphosphate-dependent phosphorylation of both D-tagatose 6-phosphate and D-fructose 6-phosphate. Although the Vmax values were equal for these two substrates, the apparent Km values differed by 10,000-fold, being 16 micro M for D-tagatose 6-phosphate and 150 mM for D-fructose 6-phosphate. The purified enzyme was free from the constitutive D-fructose-6-phosphate kinase. Phosphoryl donors used by D-tagatose-6-phosphate kinse, listed in order of decreasing rates at saturating concentrations were GTP, UTP ITP ATP, CTP, and TTP; the Km values were 0.38, 0.91, 0.17, 0.16, 18, and 20 mM, respectively. The enzyme appeared to be nonallosteric; it exhibited Michaelis-Menten kinetics and was not inhibited by high concentrations of MgATP. However, it was activated 3- to 4-fold by 33.3 mM K+, NH4+, Rb+, and Cs+, and was inhibited 31 to 65% by 33.3 mM Na+ and Li+. It was inactivated reversibly by the thiol reagent, N-ethylmaleimide. The subunit molecular weight was estimated to be 52,000, and the native enzyme appeared to be a dimer with a sedimentation coefficient of 6.8 S. Data on stability, pH optimum, and inducibility of the enzyme are also presented.

Cations, Monovalent↗

PubMed1983

Identification of the GalP galactose transport protein of Escherichia coli.

Escherichia coli strains have been isolated with a transposon 10 insertion or an amber mutation inactivating the galP gene, which specifies the galactose-H+ (GalP) transport system. Comparison of the membrane proteins between these strains and their GalP+ parents by dual isotope analysis showed that a component of Mr = 34-39,000 was consistently absent from the GalP- mutants. Galactose, methyl-beta-D-galactoside, and talose protected the GalP transport system from inactivation by N-ethylmaleimide. A membrane protein of Mr = 34-38,000 was modified by N-([2-3H]ethyl)maleimide at the binding site of these sugars. Two-dimensional gel electrophoresis of the membrane proteins has resolved a component of Mr = 35-38,000 (average apparent pI = 5.7) present in parent strains (GalP+) but not in the GalP- mutants. These observations identified a protein of apparent Mr = 37,000 as the product of the galP gene of E. coli.

Cell Membrane↗

PubMed1984

Mitogenic properties of neuraminidase and galactose oxidase-treated lymphoblastoid cells and plasma membranes for peripheral blood lymphocytes.

Generation of aldehydes on terminal D-galactose or N-acetyl-D-galactosamine residues of cell surface glycoproteins by treatment with neuraminidase and galactose oxidase (NAGO) renders some types of cells mitogenic for T lymphocytes. The cell surface molecules required for the presentation of mitogenic signals by NAGO-treated cells are unknown. We tested the mitogenic properties of NAGO-treated lymphoblastoid cell lines (LCL) and subcellular fractions as an initial step in the isolation and characterization of cell surface molecules required for stimulation. We report here that the NAGO-LCL of B cell lineage were potent stimulators, whereas the NAGO-LCL of T cell lineage were weaker and more variable stimulators of lymphocyte proliferation. T-LCL that were stimulatory in indirect stimulation did not induce a mixed lymphocyte response, whereas the B-LCL were positive in both assays. Aldehyde-bearing plasma membrane-enriched subcellular fractions, depleted of nuclear, cytosolic, and mitochondrial components, were mitogenic, and the stimulatory activity was dose dependent. The ability to induce mitogenesis was abrogated by reduction of cell surface aldehyde groups. The results indicate that lymphocyte activation, induced by NAGO-treated stimulatory cells, is a plasma membrane-associated event and does not require the metabolic activity of intact cells. Furthermore, the aldehyde moiety is required but not sufficient for presentation of mitogenic signals. The LCL provide a suitable and reproducible source for isolation and characterization of stimulatory cell surface structures.

Aldehydes↗

PubMed1984

16,16-Dimethyl prostaglandin E2 stimulates galactose and glucosamine but not serine incorporation in rat gastric mucous cells.

It has been suggested that the cytoprotective effect of prostaglandins could be mediated by an increased mucus glycoprotein secretion in the stomach. In the rat we studied the mucus glycoprotein synthesis after an in vivo treatment with 16,16-dimethyl prostaglandin E2 (10 micrograms/kg X day subcutaneously) for 1 h or 7 days. The incorporation rate of [3H]galactose, [3H]glucosamine, and [3H]serine was determined by light microscopic autoradiography in the ex vivo vascularly perfused stomach. Prostaglandin increased the rate of [3H]galactose and [3H]glucosamine incorporation twofold to fourfold in the fundic surface mucous cells; but the total protein synthesis as measured by [3H]serine incorporation was not increased. Analyses of purified mucus glycoprotein did not show an effect on carbohydrate composition, oligosaccharide chain size, nor on buoyant density, after prostaglandin treatment. The present study reveals that 16,16-dimethyl prostaglandin E2 stimulates the mucus glycoprotein synthesis in the fundic mucous cells. This effect may well be one of the mechanisms by which prostaglandin protects the stomach against noxious agents.

16,16-Dimethylprostaglandin E2↗

PubMed1984

Antibody-ricin conjugates: a method of linkage which blocks the galactose binding site of ricin.

Conjugates of the monoclonal antibody anti-Thy 1:1 (OX7) and ricin have been constructed, using a thioether bond, such that the ricin no longer can bind Sepharose or asialofetuin. These conjugates were found to be very toxic to Thy 1:1 expressing AKR-A cells whereas they showed little toxicity to Thy 1:2 expressing EL4 cells. By comparison, OX7-ricin conjugates which retained galactose-binding capability were still highly toxic to EL4 cells and this toxicity was antagonized by lactose. A second conjugate made from the W3/25 monoclonal antibody was constructed. The W3/25-ricin conjugate which had lost Sepharose-binding capacity was toxic to W3/25 antigen-expressing rat T-leukaemia cells. This is in sharp contrast to the disulphide linked W3/25-ricin A-chain conjugate which is totally inactive, suggesting that the role of the B-chain in membrane transport of the A-chain into the cytosol is independent of galactose recognition.

Animals↗

PubMed1984

Hypernatremic dehydration as a sign leading to the diagnosis of glucose-galactose malabsorption in breast-fed neonates.

Hypernatremic dehydration is described in a case of a breast-fed infant with glucose-galactose malabsorption. Hypernatremic dehydration in general is uncommon in normal breast-fed infants. The finding of hypernatremic dehydration in breast-fed infants with watery diarrhea and sugar in the stool should lead to the consideration of monosaccharide intolerance such as glucose-galactose malabsorption.

Carbohydrate Metabolism, Inborn Errors↗

PubMed1983

Galactose-induced retinal capillary basement membrane thickening: prevention by Sorbinil.

Normotensive and spontaneously hypertensive rats fed a 30% galactose diet until 15-21 months of age developed significant (P less than 0.05) retinal capillary basement membrane thickening, compared with animals fed a standard test diet. Animals on the high galactose diet containing 250 mg/kg of the aldose reductase inhibitor, Sorbinil, did not develop basement membrane thickening. No cytologic abnormalities of pericytes or endothelial cells were noted, and pericyte:endothelial cell nuclear ratios did not differ in the various experimental groups. This model reproduces a characteristic lesion of diabetes mellitus in non-diabetic animals, and should facilitate study of the biochemical mechanisms of basement membrane thickening.

Animals↗

PubMed1984

Urea excretion, galactose elimination, and aminopyrine disappearance during normal liver regeneration after partial hepatectomy. Comparison with other function tests reported.

After removal of 70% of normal rat liver, liver weight was 37% of control at 3 1/2 hours and 49% at 24 hours. Urea formation per gram liver after an NH4+ load and galactose elimination per gram liver were well-preserved during this early posthepatectomy period. At 46 hours after removal, galactose elimination was transiently less than would be expected from liver weight. The aminopyrine disappearance rate fell to 50% to 63% of control values until 72 hours, when it decreased further to 43%, disproportionately less than liver weight. The disappearance rate per gram liver at this time was 63% of control. Serum bile acid concentration increased 17-fold by 24 hours, and was five times that of control concentration at 72 hours. Comparisons of these four measures and six other in vivo measures of function previously reported permitted a segregation of the livers into two groups according to liver function after hepatectomy: those that were disproportionately preserved or were proportional to the amount of liver present, and those that were disproportionately reduced in relation to liver weight. Four additional measurements reported in isolated perfused livers after hepatectomy were similarly segregated. It appears that those liver functions that most closely reflect cellular growth or associated changes in liver blood flow are preserved, whereas those that are possibly more specialized and differentiated are depressed during regeneration.

Aminopyrine↗

PubMed1978

Coated charcoal hemoperfusion for the removal galactose in rats.

Microencapsulated activated charcoal has been used in this report to remove galactose from aqueous solution in-vitro and from blood of galactosemic rats. Coconut charcoal is not effective in removing galactose, whereas petroleum-based activated charcoal is very effective.

Adsorption↗

PubMed1981

Stimulation of chronic lymphatic leukaemia cells by pokeweed mitogen after treatment with neuraminidase-galactose oxidase.

CLL lymphocytes gave a low response upon stimulation with PHA or PWM in 3-day cultures. However, after treatment with neuraminidase-galactose oxidase (NGO), in the presence of PWM, CLL lymphocytes transformed into blasts and incorporated 3H-thymidine in 3-day cultures. This response of CLL lymphocytes was similar to that given by normal lymphocytes to PWM in 3-day cultures. The best stimulation of CLL lymphocytes was achieved when conditioned medium (CM) from normal T lymphocytes was present in PWM cultures. Purified B lymphocytes from CLL (T lymphocytes and monocytes removed) did not respond to PHA or PWM. However, after NGO treatment these cells were stimulated by PWM, but only in the presence of CM. PHA failed to stimulate NGO-treated CLL lymphocytes or purified B lymphocytes. This study shows that CLL lymphocytes, which usually fail to respond to mitogens, can be stimulated by PWM to proliferate after treatment with neuraminidase-galactose oxidase (NGO). This technique of B cell stimulation has been found useful in cytogenetic studies of B cell proliferative disorders.

B-Lymphocytes↗

PubMed1982

Hepatic galactose elimination kinetics in the intact pig.

The hepatic galactose elimination kinetics was studied in eight anaesthetized pigs by hepatic vein catheterization. Galactose was given as successive constant intravenous infusions so that steady-state concentrations, ranging from 50 mumol/l to 8 mmol/l, were obtained. Concentrations were measured in a peripheral artery and in the hepatic veins. Hepatic blood flow was determined by constant infusion of indocyanine green. The elimination kinetics is described by a mathematical model which assumes that the liver sinusoids are perfused with unidirectional blood flow and that the elimination in the hepatocytes takes place according to Michaelis-Menten kinetics. This creates a decreasing sinusoidal blood concentration from the inlet to the outlet of the liver. The estimated maximal elimination rate, Vmax, was on average 0.67 mmol min-1 kg-1 liver (range 0.55-0.95) and the half saturation concentration Km 0.25 mmol/l (0.12-0.58). The estimate of Km is similar to the value found in the isolated perfused pig liver (0.23 mmol/l), whereas the estimate of Vmax is about 50% higher (0.43 mmol min-1 kg-1 liver), probably due to both extrahepatic elimination in the splanchnic area and a better function of the liver in situ than in the isolated preparation.

Animals↗

PubMed1980

Effect of raw legume diets on intestinal absorption of D-galactose by chick.

The effect of four raw legume diets on the intestinal absorption of D-galactose and oxygen consumption were studied in chick. Field beans (Vicia faba), soybeans (Glycine soja), bitter vetch (Vicia ervilia), and navy beans (Phaseolus vulgaris), were used. The intestinal absorption was determined by both in vivo and in vitro techniques. In vivo, only navy beans and soybeans inhibit intestinal transport of D-galactose, while in vitro all the diets do. Oxygen consumption by intestinal rings increases in chicks fed on bitter vetch diet.

Animal Feed↗

PubMed1980

Lactose and D-galactose metabolism in Staphylococcus aureus. IV. Isolation and properties of a class I D-ketohexose-1,6-diphosphate aldolase that catalyzes the cleavage of D-tagatose 1,6-diphosphate.

The inducible D-ketohexose-1,6-diphosphate aldolase that functions in the metabolism of lactose and D-galactose in Staphylococcus aurues was purified to electrophoretic homogeneity from an extract of D-galactose-grown cells. At saturating substrate concentrations, D-tagatose 1,6-diphosphate was cleaved to dihydroxyacetone phosphate plus D-glyceraldehyde 3-phosphate at twice the rate of D-fructose 1,6-diphosphate; Km values for D-tagatose 1,6-diphosphate and D-fructose 12,6-diphosphate were 1.5 mM and 2.5 mM, respectively. The enzyme catalyzed the aldol condensation of dihydroxyacetone phosphate and D-glyceraldehyde 3-phosphate to yield a mixture of the 1,6-diphosphate derivatives of D-tagatose, D-fructose, D-sorbose, and D-psicose, indicating that it also catalyzes the cleavage of all four D-2-ketohexose 1,6-diphosphates. The enzyme was not inhibited by EDTA and it had no divalent metal ion requirement, but it did exhibit substrate-dependent inactivation by NaBH4, indicating that it is a Class I (Schiff's base) aldolase. Density gradient centrifugation and gel electrophoresis in the presence of sodium dodecyl sulfate indicated that the enzyme exists as a monomer with amolecular weight of about 37,000 and a sedimentation coefficient of 3.4 S. Data on the stability, pH optimum, and inducibility of the enzyme are also presented.

Aldehyde-Lyases↗

PubMed1995

Development of amebicidal cell-mediated immunity in gerbils (Meriones unguiculatus) immunized with the galactose-inhibitable adherence lectin of Entamoeba histolytica.

The galactose-inhibitable adherence lectin of Entamoeba histolytica is a protective antigen in the gerbil model of amebic liver abscess. To further understand the mechanisms of vaccine efficacy, we studied the cell-mediated immune response to the lectin in gerbils. Splenocytes harvested from immunized gerbils demonstrated in vitro proliferation and production of interleukin-2 and gamma-interferon in response to purified adherence lectin (P < 0.05 for each compared to control splenocytes). Splenocytes from immunized gerbils developed direct amebicidal activity (P = 0.014) following in vitro stimulation with the adherence lectin. Splenocytes harvested from immunized gerbils following intrahepatic challenge with viable E. histolytica adherence lectin. Splenocytes harvested from immunized gerbils following intrahepatic challenge with viable E. histolytica trophozoites demonstrated proliferative and amebicidal responses (P < 0.05). In conclusion, immunization with the E. histolytica galactose-inhibitable adherence lectin elicits an amebicidal cell-mediated response that is enhanced by parasite challenge.

Animals↗

PubMedDate not supplied

Galactose-specific lectin from Viscum album as a mediator of aggregation and priming of human platelets.

Galactose-specific lectin from Viscum album (VAA) was found to induce aggregation of human platelets in a dose- and sugar-dependent manner. Small nonaggregating concentrations of VAA primed the response of platelets to known aggregants (ADP, arachidonic acid, thrombin, ristocetin, and A23187). VAA-induced platelet aggregation was completely reversible by addition of the sugar inhibitor lactose and the platelets from disrupted aggregates maintained the response to other aggregants. The lectin-induced aggregation of washed platelets was more resistant to metabolic inhibitors than thrombin- or arachidonic acid-dependent cell interaction. In contrast to the related galactose-specific lectin from Ricinus communis and the soy bean agglutinin, the lectin did not aggregate liposomes prepared from total platelet lipids, indicating different affinities of aggregation-mediating lectins to platelet glycolipids.

Arachidonic Acid↗

PubMed1994

Assessment of sulfhydryl group in individual rat lens protein subunits during galactose cataract development.

A specific reagent DACM [N-(7-Dimethylamino-4-methyl-3-coumarinyl)maleimide] is used to study the -SH groups in lens proteins of normal and galactose cataractous rats. DACM when reacts readily with -SH groups form strong fluorescent adducts. The two -dimensional electrophoresis with DACM pre-labeled proteins is a simple and sensitive method for detecting -SH groups of protein subunit. In the present study, based on IEF/SDS-PAGE electrophoretically characterized soluble crystallins, describes specific changes in -SH groups of protein subunit during the development of galactose cataract. The contents of -SH groups of crystallins are progressively decreased in cataractous (5+) lens, the reduction of -SH content in alpha- and beta- crystallin protein subunits of the normal and cataractous lens proteins is also noticeable.

Animals↗

PubMed1994

Structure and mechanism of galactose oxidase. The free radical site.

Crystallographic and spectroscopic studies on galactose oxidase have shown that the active site involves a free radical on tyrosine 272, one of the ligands coordinated to the Cu2+ cofactor. A novel thioether bond between tyrosine 272 and cysteine 228, and a stacking tryptophan 290, over this bond, are features of the crystal structure. The present study describes the development of a high level heterologous expression system for galactose oxidase and the construction of mutational variants at these key active site residues. The expressed wild-type enzyme and mutational variants (W290H and C228G) have been characterized by x-ray crystallography, visible spectroscopy, and catalytic activity measurements. A further variant protein, Y272F, could not be purified. The data establish that the thioether bond and stacking tryptophan are essential for activity and further support a role for tryptophan 290 as a component of the free radical site.

Base Sequence↗

PubMed1994

Peripheral nerve injury induces Schwann cells to express two macrophage phenotypes: phagocytosis and the galactose-specific lectin MAC-2.

In N mice, peripheral nerve injury is followed by the normal rapid progression of Wallerian degeneration: Schwann cells proliferate and lose their myelin, which is phagocytized and metabolized by blood-borne macrophages. The role of Schwann cells in myelin phagocytosis is debated. Additionally, the molecular mechanisms underlying myelin phagocytosis by the two cell types are not well understood. To elucidate the role of Schwann cells as phagocytes we studied, electron microscopically, in vivo and in vitro degenerating, frozen, and neuroma nerve segments. The major cell types composing these tissues differed: Schwann and macrophages in in vivo degenerating; Schwann in in vitro degenerating; macrophages in frozen; Schwann, macrophages, and fibroblasts in neuroma nerve segments. Both macrophages and Schwann cells phagocytized myelin. We further studied, by immunocytochemistry and immunoblot analysis, the expression of molecules that are characteristically displayed by inflammatory and mature murine macrophages: MAC-1 (the C3b complement receptor), MAC-2 (a galactose-specific lectin), the Fc receptor, and the F4/80 antigen. All were detected in the macrophage-rich, in vivo degenerating, frozen, and neuroma nerve segments. Surprisingly, MAC-2 was also expressed in the macrophage-scarce, Schwann-rich, in vitro degenerating nerve. Immunocytochemistry and immunoblot analysis of isolated non-neuronal cells revealed that both macrophages and Schwann cells displayed MAC-2 on their surface and in their cytoplasm. Morphometry unveiled that galactose and lactose specifically inhibited myelin phagocytosis, as predicted if MAC-2 was mediating myelin phagocytosis by lectinophagocytosis (lectin-mediated phagocytosis). The role of MAC-2 in mediating myelin phagocytosis was further supported by two observations made in W mice that display very slow progression of Wallerian degeneration. First, the failure to degenerate in vivo was associated with deficient MAC-2 production. Second, degeneration that occurred in vitro was associated with MAC-2 production. Furthermore, a strong positive correlation between levels of MAC-2 expression and the extent of myelin destruction by phagocytosis was observed over a wide range of values.

Animals↗