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PubMed1987

Isolation of the galactose-binding lectin that mediates the in vitro adherence of Entamoeba histolytica.

Entamoeba histolytica adheres to human colonic mucus, colonic epithelial cells, and other target cells via a galactose (Gal) or N-acetyl-D-galactosamine (GalNAc) inhibitable surface lectin. Blockade of this adherence lectin with Gal or GalNAc in vitro prevents amebic killing of target cells. We have identified and purified the adherence lectin by two methods: affinity columns derivatized with galactose monomers or galactose terminal glycoproteins, and affinity columns and immunoblots prepared with monoclonal antibodies that inhibit amebic adherence. By both methods the adherence lectin was identified as a 170-kD secreted and membrane-bound amebic protein. The surface location of the lectin was confirmed by indirect immunofluorescence. Purified lectin competitively inhibited amebic adherence to target cells by binding to receptors on the target Chinese hamster ovary cells in a Gal-inhibitable manner.

Animals↗
PubMed1993

Effects of galactose feeding on aldose reductase gene expression.

Aldose reductase (AR) is implicated in the pathogenesis of the diabetic complications and osmotic cataract. AR has been identified as an osmoregulatory protein, at least in the renal medulla. An outstanding question relates to the response of AR gene expression to diet-induced galactosemia in extrarenal tissues. This paper shows that AR gene expression in different tissues is regulated by a complex multifactorial mechanism. Galactose feeding in the rat is associated with a complex and, on occasions, multiphasic pattern of changes in AR mRNA levels in kidney, testis, skeletal muscle, and brain. These changes are not in synchrony with the temporal sequence of changes in tissue galactitol, galactose, and myoinositol concentrations. Moreover, galactose feeding results in changes in tissue AR activities that are not related, temporally or quantitatively, to the alterations in tissue AR mRNA or galactitol levels. It is concluded that AR gene expression and tissue AR activities are regulated by mechanisms that are not purely dependent on nonspecific alterations in intracellular metabolite concentrations. This conclusion is supported by the finding that chronic xylose feeding, despite being associated with intracellular xylitol accumulation, does not result in alterations in AR mRNA levels, at least in the kidney.

Aldehyde Reductase↗
PubMed1977

The activity of galactose-1-phosphate uridyltransferase and galactokinase in human fetal organs.

The activity of galactose-1-phosphate uridyltransferase (transferase) and galactokinase in several organs from human fetuses 7-28 weeks old was measured by using radioactive substrates and column chromatography for product identification. The specific activity of transferase and galactokinase increased with gestational age and reached, at the 28th week, a maximal level of 30.0 and 7.9 nmol/min/mg protein (units) in liver, 4.7 and 2.5 units in kidney, 6.0 and 4.0 units in lung, 6.7 and 2.9 units in spleen, 5.2 and 2.6 units in cardiac muscle, and 4.0 and 1.4 units in skeletal muscle, respectively. The activity in brain, on the other hand, remained quite constant with 1.2 units in the case of transferase and 0.5 units in the case of galactokinase during this period. The activities of both enzymes in the liver of children were slightly lower than the highest fetal level during the period of pregnancy studied. Galactokinase activity in fetal erythrocytes was approximately 4 times higher and the transferase activity approximately 30% higher than in adults. The Km value of fetal liver transferase for galactose-1-phosphate was found to be 0.330-0.357 mM and that of galactokinase for galactose, 0.265-0.277 mM.

Child↗
PubMed1983

Defective galactose oxidation in a patient with glycogen storage disease and Fanconi syndrome.

Carbohydrate metabolism was studied in a child with atypical glycogen storage disease and Fanconi syndrome. Massive glucosuria, partial resistance to glucagon and abnormal responses to carbohydrate loads, mainly in the form of major impairment of galactose utilization were found, as reported in previous cases. Increased blood lactate to pyruvate ratios, observed in a few cases of idiopathic Fanconi syndrome, were not present. [1-14C]Galactose oxidation was normal in erythrocytes, but reduced in fresh minced liver tissue, despite normal activities of hepatic galactokinase, uridyltransferase, and UDP-glucose 4-epimerase in homogenates of frozen liver. These data suggest a defect in hepatic galactose metabolism not so far identified.

Child, Preschool↗
PubMed1991

Modulation of rat tissue galactose-1-phosphate uridyltransferase by uridine and uridine triphosphate.

Uridine-containing sugar nucleotides, uridine diphosphate (UDP)-glucose and UDPgalactose are important intermediates in galactose metabolism, and tissue UDPgalactose may be a salient factor in the etiology of the long-term clinical manifestations of patients with galactose-1-phosphate uridyltransferase deficient galactosemia. Because uridine and uridine nucleotides such as uridine triphosphate (UTP) are known inhibitors of rat hepatic transferase, we have examined the effects of these compounds on the activity of the enzyme in homogenates of rat brain and ovary which are target organs of galactose toxicity in classical galactosemia. In addition, the concerted effect of uridine and UTP together on hepatic transferase has been assessed. These investigations have been prompted by considerations that uridine administration may have a therapeutic role in the long-term treatment of classical galactosemia. Both uridine and UTP have been found to be potent inhibitors of brain and ovarian transferase activity. Brain enzyme activity is more sensitive to these compounds than is that of the ovary. They are competitive inhibitors of UDPglucose in both newborn and adult brain enzyme preparations with a ki of 0.15 to 0.20 mM. Uridine and UTP at low concentrations were found to have an additive effect on rat hepatic transferase activity, which is especially significant in that uridine administration is known to increase hepatic UTP concentration. These findings suggest judicious caution should be used in giving uridine to patients with genetically limited transferase activity because the possibility exists of inhibiting small amounts of residual enzyme in the tissues of affected subjects.

Animals↗
PubMed1996

Galactose-containing carbohydrates are preferentially absorbed in the neonatal pig colon.

Previous studies on the piglet colon in newborns cleared of bacterial metabolic activity showed a capacity for lactose absorption. Colonic absorption occurred at a flux rate equal to the assimilation of lactose by the small intestine but by a process that did not involve either glucose-galactose sodium cotransport or simple diffusion. Surprisingly, colonic lactose transport did not require either fermentation or cleavage of the disaccharide for uptake. Experiments were designed to test the selectivity of the colonic transport process for a variety of carbohydrates. Colonic tissues from 4-7-d-old piglets were mounted in Ussing chambers and the mucosal-to-serosal flux of radiolabeled carbohydrates was compared with that of lactose. The results showed a 3-4-fold greater flux of galactose-containing sugars as compared with glucose-containing carbohydrates at concentrations up to 40 mM. Even lactulose, a synthetic disaccharide assumed to require bacterial digestion before assimilation, was transported readily. N-Acetylgalactosamine, a component of colonic mucus, inhibited the flux of lactose, whereas N-acetylglucosamine did not. Similarly, lactosylated BSA inhibited lactose flux, whereas nonlactosylated BSA did not. The capacity of the colon of the newborn to differentiate moieties as similar as glucose and galactose suggests an absorptive process for carbohydrates with a high degree of discrimination.

Animals↗
PubMed1985

High density mammalian cell growth in Leibovitz bicarbonate-free medium: effects of fructose and galactose on culture biochemistry.

The most commonly used buffering system for mammalian cell cultures is a bicarbonate/CO2 system, which requires CO2 regulators and incubators to supply a constant level of CO2. As a replacement, Leibovitz developed a bicarbonate-free medium, L15, with relatively high levels of certain amino acids in the free base form. We found that a modified form of L15, containing 10 mM-fructose instead of galactose, supported high density growth of Vero and MDCK cells, with maintenance of a stable pH and lactate/pyruvate ratio. We report here investigations of Vero and MDCK cell growth and culture biochemistry at different concentrations of the two carbohydrates. The initial fructose concentration in the medium affected the eventual pH of the medium, the rate of production of lactic acid and ammonia, and the fructose utilization rate. The initial galactose concentration affected the growth rate but did not affect eventual culture pH, the rates of lactate and ammonia production, or the rate of its own utilization. Thus, Leibovitz' formula, modified to contain 10 mM-fructose, appears to yield satisfactory stability of culture pH and the lactate/pyruvate ratio. At all concentrations of galactose tested, the lactate/pyruvate ratio drifted out of the physiological range.

Ammonia↗
PubMed2002

Molecular basis for glucose-galactose malabsorption.

Glucose-galactose malabsorption (GGM) is an autosomal recessive disease that presents in newborn infants as a life-threatening diarrhea. The diarrhea ceases within 1 h of removing oral intake of lactose, glucose, and galactose, but promptly returns with the introduction of one or more of the offending sugars into the diet. Our goal is to determine whether or not mutations in the sodium-glucose cotransporter gene (SGLT1) are responsible for GGM. We first isolated the human cDNA (hSGLT1), mapped the gene, and identified its chromosomal location (22q13.1). Our approach was then to screen GGM patients for mutations in hSGLT1 and then determine if these caused defects in sugar transport using the Xenopus laevis oocyte expression system. In 46 patients we have identified the mutations responsible for GGM. These included missense, nonsense, frame shift, splice site, and promoter mutations. In 30 patients, the same mutations were on both alleles, and the remaining 16 had different mutations on each allele (compound heterozygotes). Several mutations (e.g., C355S) were found in unrelated patients. The nonsense, frame shift, and splice site mutations all produce nonfunctional truncated proteins. In 22 out of the 23 missense mutations tested in the oocyte expression system, the proteins were translated and were stable in the cell, but did not reach the plasma membrane. In four of these mutants, an alanine residue was replaced by a valine, and in two, the trafficking defect was rescued by changing the valine to cysteine. One mutant protein (Q457R) did reach the plasma membrane, but it was unable to transport the sugar across the cell membrane. We conclude that mutations in the SGLT1 gene are the cause of glucose-galactose malabsorption, and sugar transport is impaired mainly because the mutant proteins are either truncated or are not targeted properly to the cell membrane.

Carbohydrate Metabolism, Inborn Errors↗
PubMed2005

Combinatorial approaches to functional models for galactose oxidase.

The copper enzyme galactose oxidase (GOase, EC 1.1.3.9) catalyses the oxidation of D-galactose and other primary alcohols in air to the corresponding aldehydes and hydrogen peroxide. The current mechanistic hypothesis for this two-electron redox reaction involves a Cu(I)/Cu(II) couple and the reversible oxidation of a ligating phenolate (tyrosine residue of the Tyr272-Cys228 conjugate) to a phenoxyl radical. Our approaches to functional models for galactose oxidase comprise both the use of low-molecular-weight copper complexes of a Schiff-base and sulfonamide ligands, and the synthesis/screening of combinatorial libraries. With regard to the latter, we have synthesized (by the IRORI-directed synthesis approach) peptide libraries carrying either His or the redox-active amino acids Tyr, mod-Cys (a model for the Tyr272-Cys228 conjugate) or TOAC (a TEMPO-derived alpha-amino acid) at four variable positions. After incubation with copper ions, the catalytically active library members were identified by specially designed screening methods.

Biomimetics↗
PubMed1985

Carbohydrate-containing derivatives of the trypsin-kallikrein inhibitor aprotinin from bovine organs. II. Inhibitor coupled to the (carboxymethyl)dextran derivatives of D-galactose.

The trypsin-kallikrein inhibitor aprotinin was coupled to (carboxymethyl)dextran derivatives of D-galactose. The conjugates contained 14 and 38 D-galactose residues/mol of protein, respectively. The apparent dissociation constants Ki of the complexes between trypsin and modified aprotinins proved to be one order of magnitude higher than the respective values for native aprotinin. The distribution of the modified aprotinins in rat organs after endocardial injection has been studied. The conjugates of aprotinin with (carboxymethyl)dextran derivatives of D-galactose were characterized by decreased clearance rates; they accumulated in the active form in liver. The accumulation was 2.5-10 times higher than native aprotinin for the time of observation (5 min-2 h).

Animals↗
PubMed1992

The influence of alpha- and beta-galactose residues and sialic acid O-acetyl groups of rat erythrocytes on the interaction with peritoneal macrophages.

The significance of glycoconjugates on the surface of rat erythrocytes was studied in the interaction of these cells with homologous peritoneal macrophages. The erythrocytes exposing terminal alpha-galactose and thus of B blood group specificity, as well as sialic acid are not bound by the macrophages. beta-Galactose residues exposed by sialidase induced strong binding and additional alpha-galactosidase treatment enhanced the binding. beta-Galactose exposed on glycolipids after pronase and alpha-galactosidase treatment induced no binding. An intact protein core of the glycoproteins on the erythrocyte surface was necessary for interaction with macrophages. Partial de-O-acetylation of sialic acids prior to sialidase treatment stimulated subsequent binding of the erythrocytes.

Acetylation↗
PubMedDate not supplied

The effect of galactose metabolic disorders on rat brain Na+,K+-ATPase activity.

To evaluate the effect of galactose metabolic disorders on the brain Na+,K+-ATPase in suckling rats. Separate preincubations of various concentrations (1-16 mM) of the compounds galactose-1-phosphate (Gal-1-P) and galactitol (galtol) with whole brain homogenates at 37 degrees C for 1 h resulted in a dose dependent inhibition of the enzyme whereas the pure enzyme (from porcine cerebral cortex) was stimulated. Glucose-1-phosphate (Glu-1-P) or galactose (Gal) stimulated both rat brain Na+,K+-ATPase and pure enzyme. A mixture of Gal-1-P (2 mM), galtol (2 mM) and Gal (4 mM), concentrations commonly found in untreated patients with classical galactosemia, caused a 35% (p < 0.001) rat brain enzyme inhibition. Additionally, incubation of a mixture of galtol (2 mM) and Gal (1 mM), which is usually observed in galactokinase deficient patients, resulted in a 25% (p < 0.001) brain enzyme inactivation. It is suggested that: a) The indirect inhibition of the brain Na+,K+-ATPase by Gal-1-P should be due to the presence of the epimer Gal and phosphate and that the pure enzyme direct activation by Gal-1-P and Glu-1-P to the presence of phosphate only. b) The observed brain Na+,K+-ATPase inhibitions in the presence of toxic concentrations of Gal-1-P and/or galtol could modulate the neural excitability, the metabolic energy production and the catecholaminergic and serotoninergic system.

Animals↗
PubMed1976

Role of galactose in the antigenic properties of thyroglobulin.

Thyroglobulins (TG) from a "hot" human thyroid nodule and from Fisher rats have been purified and the effects of progressive removal of sialic acid and galactose on the immunoreactive properties of the proteins were studied. Terminal sialic acid and galactose were released by stepwise hydrolysis with neuraminidase and beta-galactosidase. Agalacto-TG shows a slower electrophoretic mobility than native TG, but in polyacrylamide gel electrophoresis and immunoelectrophoresis it migrates in the same position as asialo-TG. In immunodiffusion agalacto-TG forms a spur with native TG and asialo-TG when tested against anti 19S native TG or anti-asialo-TG sera. It is thus shown that galactose in the terminal environment of the oligosaccharide chains of thyroglobulin is essential for the structural groups involved in the antigenic properties of thyroglobulin.

Animals↗
PubMed1977

Glycosyltransferase and UDP-galactose pyrophosphatase activities in the endometrium during oestrous cycle of the rat.

UDP-galactose: glycoprotein galactosyltransferase, CMP-sialic acid: glycoprotein sialyltransferase and UDP-galactose pyrophosphatase activities were measured in the endometrium of rat uteri during the oestrous cycle. The galactosyltransferase activity started to increase at dioestrus and reached a maximum on the afternoon of pro-estrus. The UDP-galactose pyrophosphatase activity changed in a direction opposite to that of galactosyltransferase. The sialyltransferase activity was low during metoestrus and dioestrus, but began to rise on the morning of pro-oestrus, reaching a peak on the morning of oestrus. Previously, we have shown that oestradiol administration stimulated galactosyl- and sialyltransferase and inhibited pyrophosphatase activities several-fold in the endometrium of ovariectomized rats. Progesterone prevented the oestradiol effect on the enzymes. The changes in glycosyltransferase and pyrophosphatase activities during the oestrous cycle possibly bear a direct relationship to the ovarian hormones in the rat during the normal oestrous cycle. This relationship will then be conducive to increased synthesis of glycopolymers during ovulation. Furthermore, the lag of 18 h for a maximal rise of sialyltransferase following that of galactosyltransferase is consistent with the normal sequence of glycosylation that occurs in glycoprotein secretion.

Animals↗
PubMed1984

Maintenance of neonatal rat B cells in glucose-depleted medium: effect of medium with galactose and 2-deoxyglucose.

Monolayer cultures of the pancreas of the neonatal rat were maintained for 7 days in glucose-depleted TCM 199 medium, supplemented with 5.5 mmol galactose/l, with or without 0.1 mmol 2-deoxyglucose/l. Under culture conditions without 2-deoxyglucose, the responsiveness of B cells supported on galactose was totally abolished by day 7 of culture, and islets degenerated. In contrast, the addition of 2-deoxyglucose to the galactose-supplemented medium promoted the survival and the function of B cells even in a glucose-depleted environment and, in addition, yielded the monolayers mostly consisting of endocrine cells by destroying fibroblasts selectively. On day 7 the recovery of insulin in the cells was higher than that of the cells grown in medium with galactose alone (10.7-fold), and than the initial level at day 0 (twofold). Furthermore, the response to an acute challenge with 16.7 mmol glucose/l was 3.3-fold, to 10 mmol leucine/l it was 8.5-fold, and to 10 mmol 2-ketoisocaproate/l it was 10.9-fold above each value observed on day 1. In summary, the above data indicate that morphologically intact, functionally competent endocrine B cells can be grown in medium free from glucose.

Animals↗
PubMed2026

Development and internal validation of a six-gene prognostic model based on galactose metabolism for overall survival in lung adenocarcinoma.

BACKGROUND: Lung cancer remains a leading cause of cancer incidence and mortality globally. Metabolic reprogramming promotes tumor progression and shapes an immunosuppressive tumor microenvironment. Galactose metabolism is involved in multiple malignancies, but its prognostic value in lung adenocarcinoma (LUAD) remains unclear. This study aimed to develop and internally validate a galactose metabolism-related multigene prognostic model for LUAD. METHODS: A retrospective prognostic model development and internal validation study was performed using RNA sequencing (RNA-seq) and clinical data from 585 LUAD patients in The Cancer Genome Atlas (TCGA). Differential expression, functional enrichment, univariate and multivariate Cox regression were applied to construct a prognostic gene signature. Internal validation was performed using bootstrap resampling. Model performance was evaluated by time-dependent receiver operating characteristic (ROC), C-index, calibration, and Kaplan-Meier analysis. Associations between the model and immune infiltration, immunotherapy responsiveness, and tumor stemness were also analyzed. RESULTS: A six-gene prognostic model (GALT, GANC, PGM1, GALM, B4GALT1, PGM2) was developed. The model showed good discrimination with 1-, 3-, and 5-year area under the curve (AUC) values of 0.719, 0.693, and 0.684, respectively. The low-risk group exhibited significantly longer survival, increased antitumor immune infiltration (CD8+ T cells, M1 macrophages, activated CD4+ memory T cells), higher expression of T cell proliferation-related genes, lower immune checkpoint expression, better predicted immunotherapy response, and lower tumor stemness compared with the high-risk group. CONCLUSIONS: We developed and internally validated a six-gene prognostic model for LUAD based on galactose metabolism. The model shows moderate prognostic performance and is associated with antitumor immunity and tumor stemness. It may be used for prognostic risk stratification and to guide personalized immunotherapy in LUAD.

Galactose metabolism↗
PubMed1983

The x-ray structure of the periplasmic galactose binding protein from Salmonella typhimurium at 3.0-A resolution.

The x-ray structure of the periplasmic galactose binding protein from Salmonella typhimurium, the specific receptor for taxis toward, and high-affinity transport of, galactose has been solved at 3.0-A resolution using multiple isomorphous replacement. The path of the polypeptide chain has been traced, and a model structure consisting of 292 amino acids has been fit to the electron density map. The overall shape of the molecule is that of a prolate ellipsoid, with dimensions 35 X 35 X 65 A. The protein consists of two similar domains of roughly equal size, related by an axis of pseudosymmetry, and separated by a deep cleft about 8 A wide. Each domain has a core of parallel beta sheet surrounded by five alpha helices, built by alternating strands of sheet and helix in a repeating pattern. Approximately 36% of the residues are involved in alpha helices, and 27% in beta sheet. The tertiary structure has been compared to that of the Escherichia coli arabinose binding protein (Gilliland, G.L., and Quiocho, F. A. (1981) J. Mol. Biol. 146, 341-362), a periplasmic receptor which is involved in transport, but not in chemotaxis. The overall folding of these two molecules is very similar, with the exception of two areas on the surface of the molecule on the long sides of the prolate ellipsoid. The observed variations are adequate to explain the differences in interaction of L-arabinose binding protein and galactose binding protein with the membrane proteins for transport and chemotaxis.

Calcium-Binding Proteins↗
PubMed1989

D-galactose absorption for the whole intestinal surface after different types of resection and bypass.

In vivo D-galactose absorption by the whole intestine between duodenum and rectum was studied in rats 1 month after sham operation, 50% proximal resection, intestinal bypass, or 50% distal resection. The total serosal areas were evaluated by means of an integrative method, obtaining reduced surfaces in resected or bypassed animals as compared with controls. The rate of D-galactose absorption, measured within 10 min, increased after proximal resection and bypass and diminished after distal resection, although the level was similar to that of controls at higher substrate concentrations. When expressed as serosal area, results in proximal and bypassed animals were higher than in controls, without differences (at lower galactose concentrations), and increased (at 25 mM), after distal resection. The total absorptive capacity related to wet and dry weight showed no differences in proximal and bypassed groups and a decrease after distal resection. The above results confirm a good level of recuperation when proximal intestinal surface is excluded. In case of ileal extirpation, a smaller compensatory response was found, which would be compensated for by a high substrate concentration in the intestinal lumen.

Animals↗