Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “GALACTOSE”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,675 records · Page 93Linked to original sources
PubMed1968

Fermentation of glucose, lactose, galactose, mannitol, and xylose by bifidobacteria.

For six strains of Bifidobacterium bifidum (Lactobacillus bifidus), fermentation balances of glucose, lactose, galactose, mannitol, and xylose were determined. Products formed were acetate, l(+)-lactate, ethyl alcohol, and formate. l(+)-Lactate dehydrogenase of all strains studied was found to have an absolute requirement for fructose-1,6-diphosphate. The phosphoroclastic enzyme could not be demonstrated in cell-free extracts. Cell suspensions fermented pyruvate to equimolar amounts of acetate and formate. Alcohol dehydrogenase was shown in cell-free extracts. Possible explanations have been suggested for the differences in fermentation balances found for different strains and carbon sources. By enzyme determinations, it was shown that bifidobacteria convert mannitol to fructose-6-phosphate by an inducible polyol dehydrogenase and fructokinase. For one strain of B. bifidum, molar growth yields of glucose, lactose, galactose, and mannitol were determined. The mean value of Y (ATP), calculated from molar growth yields and fermentation balances, was 11.3.

Alcohol Oxidoreductases↗
PubMed1993

Gal80 proteins of Kluyveromyces lactis and Saccharomyces cerevisiae are highly conserved but contribute differently to glucose repression of the galactose regulon.

We cloned the GAL80 gene encoding the negative regulator of the transcriptional activator Gal4 (Lac9) from the yeast Kluyveromyces lactis. The deduced amino acid sequence of K. lactis GAL80 revealed a strong structural conservation between K. lactis Gal80 and the homologous Saccharomyces cerevisiae protein, with an overall identity of 60% and two conserved blocks with over 80% identical residues. K. lactis gal80 disruption mutants show constitutive expression of the lactose/galactose metabolic genes, confirming that K. lactis Gal80 functions in essentially in the same way as does S. cerevisiae Gal80, blocking activation by the transcriptional activator Lac9 (K. lactis Gal4) in the absence of an inducing sugar. However, in contrast to S. cerevisiae, in which Gal4-dependent activation is strongly inhibited by glucose even in a gal80 mutant, glucose repressibility is almost completely lost in gal80 mutants of K. lactis. Indirect evidence suggests that this difference in phenotype is due to a higher activator concentration in K. lactis which is able to overcome glucose repression. Expression of the K. lactis GAL80 gene is controlled by Lac9. Two high-affinity binding sites in the GAL80 promoter mediate a 70-fold induction by galactose and hence negative autoregulation by Gal80. Gal80 in turn not only controls Lac9 activity but also has a moderate influence on its rate of synthesis. Thus, a feedback control mechanism exists between the positive and negative regulators. By mutating the Lac9 binding sites of the GAL80 promoter, we could show that induction of GAL80 is required to prevent activation of the lactose/galactose regulon in glycerol or glucose plus galactose, whereas the noninduced level of Gal80 is sufficient to completely block Lac9 function in glucose.

Amino Acid Sequence↗
PubMed2005

Dynamical remodeling of the transcriptome during short-term anaerobiosis in Saccharomyces cerevisiae: differential response and role of Msn2 and/or Msn4 and other factors in galactose and glucose media.

In contrast to previous steady-state analyses of the O(2)-responsive transcriptome, here we examined the dynamics of the response to short-term anaerobiosis (2 generations) in both catabolite-repressed (glucose) and derepressed (galactose) cells, assessed the specific role that Msn2 and Msn4 play in mediating the response, and identified gene networks using a novel clustering approach. Upon shifting cells to anaerobic conditions in galactose medium, there was an acute ( approximately 10 min) yet transient (<45 min) induction of Msn2- and/or Msn4-regulated genes associated with the remodeling of reserve energy and catabolic pathways during the switch from mixed respiro-fermentative to strictly fermentative growth. Concomitantly, MCB- and SCB-regulated networks associated with the G(1)/S transition of the cell cycle were transiently down-regulated along with rRNA processing genes containing PAC and RRPE motifs. Remarkably, none of these gene networks were differentially expressed when cells were shifted in glucose, suggesting that a metabolically derived signal arising from the abrupt cessation of respiration, rather than O(2) deprivation per se, elicits this "stress response." By approximately 0.2 generation of anaerobiosis in both media, more chronic, heme-dependent effects were observed, including the down-regulation of Hap1-regulated networks, derepression of Rox1-regulated networks, and activation of Upc2-regulated ones. Changes in these networks result in the functional remodeling of the cell wall, sterol and sphingolipid metabolism, and dissimilatory pathways required for long-term anaerobiosis. Overall, this study reveals that the acute withdrawal of oxygen can invoke a metabolic state-dependent "stress response" but that acclimatization to oxygen deprivation is a relatively slow process involving complex changes primarily in heme-regulated gene networks.

Algorithms↗
PubMed1984

Toxicity of 2-deoxygalactose to Saccharomyces cerevisiae cells constitutively synthesizing galactose-metabolizing enzymes.

Analysis of 400 independent spontaneous mutations conferring 2-deoxygalactose resistance upon cells constitutive for the galactose pathway suggests that toxicity is due to 2-deoxygalactose-1-phosphate. Selection for and against growth on galactose in the same strain is now possible; application to systems with transcriptional or translational gene fusions to galactokinase are discussed.

Carbohydrate Epimerases↗
PubMed1984

Carbohydrate-binding protein 35: identification of the galactose-specific lectin in various tissues of mice.

In previous studies, a lectin designated as carbohydrate-binding protein 35 (CBP35) has been isolated from cultured mouse 3T3 fibroblasts. In this study, antibodies directed against CBP35 were used to screen for cross-reactive proteins in various cultured cells and in various organs and tissues of mice. Cross-reactive proteins of the same molecular weight (Mr, 35,000) were found in human, mouse, and chicken fibroblasts and in a macrophage-like cell line, P388D1. Similarly, cross-reactive proteins were also found in the embryonic liver, lung, spleen, thymus, skin, and muscle tissue and in the lung, artery, thymus, and spleen of the adult mouse. Fractionation of extracts of mouse lung on affinity columns of asialofetuin-Sepharose yielded a protein whose molecular weight, carbohydrate-binding specificity, and immunological properties suggest that it is CBP35 derived from the lung, hereafter designated CBP35 (lung). The binding of 125I-labeled CBP35 (lung) to rabbit erythrocytes was quantitated in the presence and absence of various carbohydrates. It was found that only carbohydrates containing galactose were inhibitors of the binding; the disaccharide lactose was 100-fold more potent as an inhibitor than was the monosaccharide galactose. When extracts of the adult mouse liver were fractionated by asialofetuin-Sepharose chromatography, only a protein corresponding to CBP16 was isolated; no CBP35 was found. These results corroborate the immunoblotting data, which indicated that CBP35 was not detectable in the adult mouse liver.

Amino Acids↗
PubMed1985

DNase I-hypersensitive sites in the galactose gene cluster of Saccharomyces cerevisiae.

Five DNase I-hypersensitive regions were associated with the Saccharomyces cerevisiae galactose gene cluster during both galactose induction and glucose repression of transcription. Four hypersensitive regions were located in areas flanking the GAL cluster genes, and one site occurred within GAL10. A DNase I-hypersensitive region located between the 5' ends of divergently transcribed GAL10 and GAL1 contained sequences essential for the transcription of both genes.

Base Sequence↗
PubMed1988

GAL11 protein, an auxiliary transcription activator for genes encoding galactose-metabolizing enzymes in Saccharomyces cerevisiae.

Normal function of the GAL11 gene is required for maximum production of the enzymes encoded by GAL1, GAL7, and GAL10 (collectively termed GAL1,7,10) in Saccharomyces cerevisiae. Strains bearing a gal11 mutation synthesize these enzymes at 10 to 30% of the wild-type level in the induced state. In a DNA-RNA hybridization experiment, the gal11 effect was shown to be exerted at the transcription level. Yeast cells bearing the gal11 mutation were shown to grow on glycerol plus lactate more slowly than the wild type. We isolated recombinant plasmids carrying the GAL11 gene by complementation of the gal11 mutation. When the GAL11 locus was disrupted by insertion of the URA3 gene, the resulting yeast cells (gal11::URA3) exhibited phenotypes almost identical to those of the gal11 strains, with respect to both galactose utilization and growth on nonfermentable carbon sources. Deficiency of Gal4, the major transcription activator for GAL1,7,10, was epistatic over the gal11 defect. The Gal11 deficiency lowered the expression of GAL2 but not that of MEL1 or GAL80; expression of these genes is also known to be dependent on GAL4 function. We determined the nucleotide sequence of GAL11, which is predicted to encode a 107-kilodalton protein with stretches of polyglutamine and poly(glutamine-alanine). An alpha-helix-beta-turn-alpha-helix structure was found in a distal part of the predicted amino acid sequence. A possible role of the GAL11 product in the regulation of galactose-inducible genes is discussed.

Amino Acid Sequence↗
PubMed1983

Partial galactose disorders in families with premature cataracts.

Minor and major deficiencies of enzymes affecting galactose metabolism may be associated with cataracts of early onset. Results are presented for 10 such families with minor enzymatic disorders. Expression of the major disorders probably involves galactitol accumulation and osmotic lens damage but this mechanism is not obviously associated with minor disorders. The observed incidence of minor incomplete enzymatic disorders of galactose metabolism in families with an incidence of cataracts of early onset may be at least partly incidental.

Adolescent↗
PubMed1976

Influence of specific dietary sugars on the jejunal mechanisms for glucose, galactose, and alpha-methyl glucoside absorption: evidence for multiple sugar carriers.

The effects of feeding glucose, galactose, and alpha-methyl glucoside on the kinetics of absorption of these sugars in the jejunum of the fasting rat were assessed by recently developed chemical and electrical methods for characterizing the electrogenic active transfer mechanisms in vivo. The parameters of 'apparent Km' (an index of carrier affinity) and Vmax (an index of the maximum jejunal transfer capacity) were obtained from the kinetic data to describe quantitatively the active transport mechanisms in rats fed their normal solid diet, in rats deprived of solid food for three days, and in rats deprived of solid food but allowed ad libitum access to isotonic solutions of glucose, galactose, or alpha-methyl glucoside for up to three days. Feeding the sugars to fasting rats produced complex differential effects on the 'apparent Km's' and Vmax's of the various transport mechanisms. The changes, although complex, can best be explained by alterations in the transport mechanisms per se rather than by non-specific changes in intestinal morphology or metabolism. The differential effects induced by the feeding sugars are further evidence for the concept that jejunal enterocytes possess multiple carriers or mechansims for the absorption of actively transported sugars in vivo. The multiple forms of the sugar carriers (isocarriers?) MAY BE INVOLVED IN THE FACULTATIVE RESPONSES OF THE ENTEROCYTES TO CHANGES IN THE DIETARY LEVELS OF SUGAR AND MAY BE IMPORTANT IN UNDERSTANDING THE INFLUENCES OF DISEASE AND NUTRITIONAL STATUS ON ABSORPTION PROCESSES IN MAN.

Animals↗
PubMed1978

Analysis of the effects of food and of digestive secretions on the small intestine of the rat: III. Mucosal mass, activity of brush border enzymes, and in vivo absorption of galactose, sodium, and potassium.

A modified Roux-en-y repositioning of rat proximal small intestine resulted in a gut segment (A) exposed only to digestive secretions, but not to food and a gut segment (B) exposed to food, stomach juice and by reflux only to digestive secretions, and a third segment (C) exposed to both, food and digestive secretions. The changes in segment A were qualitatively very similar to those occurring after removal of luminal nutrition (intravenous feeding, self-emptying blind loop, and Thiry Vella loop). These findings support the hypothesis that the presence of luminal nutrition is a major factor regulating mucosal mass and enzyme activity in rat proximal small intestine. The changes in the luminal environment in segment B caused an increase in mucosal mass (in the proximal half only), an increase in sucrase activity which paralleled the increase in mucosal mass, and no change in activity of alkaline phosphatase which in fact was a decrease in activity ;at the cellular level'. Later on the net absorption of sodium and potassium was improved and the disappearance of galactose was unchanged when referred to unit length of small intestine.In segment C there was a small increase in mucosal mass, an increase in activity only for alkaline phosphatase, and an improvement of the net absorption of sodium without changes in the disappearance of galactose. These changes were compatible with a more proximal promotion of a distal gut segment.

Alkaline Phosphatase↗
PubMed1987

Effect of chronic ethanol intake on lactase activity and active galactose absorption in rat small intestine.

The effects of feeding a nutritionally adequate liquid diet containing 5% ethanol to rats over a four week period on intestinal lactase activity and the kinetics of jejunal galactose absorption in vivo have been determined. Both lactase activity and the maximum capacity for active, saturable galactose absorption (Jmax) were increased significantly after chronic ethanol ingestion. In contrast, uptake of the sugar via the phlorhizin-insensitive (passive) route was unaffected by ethanol. Our results imply the presence of an increased maturity of the enterocyte population on the villus surface in response to ethanol. The relevance of this work to uptake studies in alcoholics is briefly discussed.

Animals↗
PubMed1988

Glucose-galactose malabsorption: demonstration of specific jejunal brush border membrane defect.

Jejunal brush border glucose transport was studied in a patient with glucose-galactose malabsorption and in controls, using jejunal brush border membrane vesicles (BBMV) prepared from conventional jejunal biopsies. Whereas BBMV from controls showed a seven-fold enhancement of D-glucose uptake in the presence of an inwardly directed sodium gradient compared with its absence, no such enhancement was seen in the patient's vesicles. In BBMV from the patient, initial D-glucose uptake under sodium gradient conditions was only 10% of the mean control value. In contrast, sodium/proton exchange in BBMV from the patient was intact. These data provide the first unequivocal evidence that the jejunal brush border membrane is the site of a specific defect in sodium dependent glucose transport in glucose-galactose malabsorption. Measurement of glucose uptake by BBMV may well be the optimal diagnostic technique in this disorder.

Galactose↗
PubMed2000

Growth kinetics of Escherichia coli with galactose and several other sugars in carbon-limited chemostat culture.

Kinetic models for microbial growth describe the specific growth rate (mu) as a function of the concentration of the growth-limiting nutrient (s) and a set of parameters. A typical example is the model proposed by Monod, where mu is related to s using substrate affinity (Ks) and the maximum specific growth rate (mu max). The preferred method to determine such parameters is to grow microorganisms in continuous culture and to measure the concentration of the growth-limiting substrate as a function of the dilution rate. However, owing to the lack of analytical methods to quantify sugars in the microgram per litre range, it has not been possible to investigate the growth kinetics of Escherichia coli in chemostat culture. Using an HPLC method able to determine steady-state concentrations of reducing sugars, we previously have shown that the Monod model adequately describes glucose-limited growth of E. coli ML30. This has not been confirmed for any other sugar. Therefore, we carried out a similar study with galactose and found steady-state concentrations between 18 and 840 micrograms.L-1 for dilution rates between 0.2 and 0.8.h-1, respectively. With these data the parameters of several models giving the specific growth rate as a function of the substrate concentration were estimated by nonlinear parameter estimation, and subsequently, the models were evaluated statistically. From all equations tested, the Monod model described the data best. The parameters for galactose utilisation were mu max = 0.75.h-1 and Ks = 67 micrograms.L-1. The results indicated that accurate Ks values can be estimated from a limited set of steady-state data when employing mu max measured during balanced growth in batch culture. This simplified procedure was applied for maltose, ribose, and fructose. For growth of E. coli with these sugars, mu max and Ks were for maltose 0.87.h-1, 100 micrograms.L-1; for ribose 0.57.h-1, 132 micrograms.L-1, and for fructose 0.70.h-1, 125 micrograms.L-1.

Culture Media↗
PubMed1975

Isolation and characterization of a bacteriophage infective for a UDP-galactose-4-epimeraseless mutant of Escherichia coli.

A DNA bacteriophage, designated CP13, was isolated against Escherichia coli J5, a UDP-galactose-4-epimeraseless mutant of E. coli 0111:B4. Bacteriophage CP13 appears to be specific for rough bacterial strains. Adsorption studies with E. coli J5 grown with galactose show that the bacteriophage will not adsorb when complete lipopolysaccharide is present in the cell membrane. This indicates that lipopolysaccharide may be directly or indirectly involved with the receptor site for bacteriophage CP13. The bacteriophage DNA has a G + C content of 52%.

Adsorption↗
PubMed1976

The metabolism of carbohydrates by extremely halophilic bacteria: identification of galactonic acid as a product of galactose metabolism.

Cell-free extracts prepared from the extremely halophilic bacterium Halobacterium saccharovorum oxidize galactose and accumulate a product which reacts as if it were a lactone. The product does not act as a reducing sugar and contains all six of the carbon atoms initially present in galactose. The product was jugged to be galactonic acid, based on the behavior of the acetylmethyl ester derivative of the product and the pentaacetyl derivative of the galactonic methyl ester during gas chromatography.

Alcohol Oxidoreductases↗
PubMed1982

Selection of temperature-resistant mutants of Chinese hamster cells for growth on D-galactose.

Somatic cell variants of Chinese hamster V79 were selected for rapid growth on D-galactose at high temperatures. Their phenotypes are stable after many generations in the absence of selection pressure. They clone in D-galactose at temperatures at which the wild type cannot, while in D-glucose, the variants and the wild type appear to have the same growth properties. The use of such variants should be very important for the study of gene regulation of carbohydrate metabolism in mammalian cells.

Animals↗
PubMed1987

Effects of liver blood flow on hepatic uptake kinetics of galactose in anesthetized cats: parallel tube model.

Hepatic galactose uptake in cats anesthetized with pentobarbital was determined during (i) steady-state infusions at several doses, (ii) rapidly increasing infusion rates at different blood flows, and (iii) prolonged infusion of a single dose at different blood flows. The hepatic venous long-circuit technique was used to allow frequent sampling of arterial, portal, and hepatic venous blood without depletion of the animal's blood volume and to allow measurement and alteration of total hepatic blood flow. Uptake was shown to follow Michaelis-Menten kinetics and was consistent with the "parallel tube model." The kinetic parameters Vmax and Km could be determined under steady-state and nonsteady-state conditions and were independent of hepatic blood flow over the range 60-150% of control flow. Mean Vmax was 80 mumol/(min X 100 g liver) and mean Km was 215 microM. Vmax declined by 50% when flow was reduced to half normal. It is concluded that the parallel tube model can be used to describe and predict hepatic galactose kinetics in anesthetized cats, although other models may fit the data equally well.

Animals↗
PubMed1999

Effect of insulin-like growth factor I on in vivo intestinal absorption of D-galactose in cirrhotic rats.

Insulin-like growth factor I (IGF-I) bioavailability is reduced in liver cirrhosis, a condition frequently associated with malnutrition. We have analyzed in vivo absorption of D-galactose by jejunal loops in rats with CCl4-induced liver cirrhosis and the influence of IGF-I on intestinal sugar transport in this disease. Two different study protocols were followed. In protocol 1, healthy control rats or cirrhotic rats received saline or IGF-I (2 micrograms . 100 g body wt-1. day-1) for 2 wk. In protocol 2, control and cirrhotic rats received saline or IGF-I as a bolus injection of 1 microgram/100 g body wt followed by continuous infusion of the same dose for 100 min. In vivo D-galactose absorption was reduced in cirrhotic rats compared with healthy controls. IGF-I, as both a chronic (protocol 1) and acute treatment (protocol 2), was able to improve sugar transport in cirrhotic rats but had no effect on sugar absorption in healthy rats. A significant elongation of enterocyte microvilli was observed in cirrhotic animals; this alteration was totally or partially corrected by chronic or acute IGF-I administration. Our results show that in vivo jejunal sugar transport and microvilli structure are altered in liver cirrhosis and that IGF-I, among other effects, may correct these changes by modulating cytoskeletal organization in enterocytes.

Animals↗