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PubMed1991

[Study of galactose-1-phosphate uridyltransferase activity in erythrocytes of patients with presenile cataract].

In connection with the increased incidence of cataract in middle-aged patients investigations were carried out in order to clear up one of the possible causes of this condition. The detection of a substantial decrease of galactose-1-phosphate uridyl transferase activity in patients with presenile cataract evidences the disturbance of galactose metabolism these patients and allows to accept this genetic defect as the causes of opacification of the lens. Attention was called to the eventual importance of these investigations because of the adoption of a diet without galactose in person threatened+ by cataract could prevent or check this disease.

Adolescent↗
PubMed1985

Red blood cells galactose-1-P-urydil transferase in senile and presenile cataracts.

There are conflicting reports in the literature regarding the role of partial deficiency of "galactosemic" enzymes (galactose-1-P-urydil transferase and galactokinase) in the development of infantile and presenile cataract. The AA. have investigated the levels of Red Blood Cell Galactose-1-P-urydil transferase in 39 cataractous patients and in 22 age matched controls. A weak correlation between the enzymatic activity deficiency and the presenile cataract has been identified. The results suggest that a chronic impairment of galactose metabolism may be a contributory risk factor in the pathogenesis of presenile cataracts; however, further investigations are required to assess the actual significance of the findings of the present paper.

Adult↗
PubMed1988

Retinoic acid-induced differentiation of the mouse teratocarcinoma cell line F9 is accompanied by an increase in the activity of UDP-galactose: beta-D-galactosyl-alpha 1,3-galactosyltransferase.

We report here that both the mouse teratocarcinoma F9 cells and F9 cells induced to differentiate by treatment with retinoic acid contain cell surface glycoconjugates with terminal alpha-linked galactose residues, as shown by agglutination of cells with antisera to blood type B, but not to type A. In addition, both cell types contain high numbers of binding sites for Griffonia simplicifolia-I, a lectin which binds to terminal alpha-linked galactose residues, although differentiated F9 cells contain approximately 50% more binding sites/cell for this lectin. We have also confirmed that differentiation is accompanied by a decrease in the expression of the fucose-containing stage-specific embryonic antigen (SSEA)-1, as evidenced by the fact that F9 cells, but not differentiated F9 cells, are agglutinated by monoclonal antibody to this antigen. Since these results indicate that surface glycoconjugates contain terminal alpha-linked galactose residues, we assayed cell extracts for the enzyme UDP-Gal:beta-D-Gal-alpha 1,3-galactosyltransferase. We have found that F9 cell extracts contain this activity, and differentiation results in a significant increase in the specific activity of the enzyme, from approximately 2 nmol/mg h in F9 extracts to 7 nmol/mg h in RA/F9 extracts. It has been suggested that the loss of the SSEA-1 antigen upon differentiation of F9 cells is due to decreased activity of the enzyme GDP-Fuc:beta-D-GlcNAc-alpha 1, 3-fucosyltransferase. We therefore determined the activities of this fucosyltransferase and several other glycosyltransferases, which included UDP-GlcNAc:beta-D-Gal-beta 1,3-N-acetylglucosaminyltransferase, UDP-Gal:beta-D-GlcNAc-beta 1,4-galactosyltransferase, and GDP-Fuc:beta-D-GlcNAc-alpha 1,6-fucosyltransferase. We have found that extracts from both cell types contain these enzyme activities; differentiation, however, does not result in substantial changes in any of these activities.

Agglutination↗
PubMed1987

Major and minor forms of the rat liver asialoglycoprotein receptor are independent galactose-binding proteins. Primary structure and glycosylation heterogeneity of minor receptor forms.

Preparations of the rat liver asialoglycoprotein receptor (rat hepatic lectin, RHL), which is responsible for the selective uptake of partially deglycosylated serum glycoproteins, have been found to contain multiple polypeptide species. A method has been developed for separating the predominant species (RHL-1) from the minor species (RHL-2/3) using conditions in which RHL-1 retains its galactose-binding activity. Endoglycosidase digestion and lectin blotting have been utilized to demonstrate that RHL-2 and RHL-3 differ by the presence of different carbohydrate structures attached to a common peptide backbone. Antisera specific for RHL-1 and RHL-2/3 have been prepared and utilized to analyze the results of cross-linking experiments performed on purified receptor and hepatocyte membranes. The results show that RHL-1 and RHL-2/3 polypeptides are each associated into homooligomers but are physically unlinked to each other. The structure of the RHL-2/3 polypeptide has been established by protein and cDNA sequence analysis, which reveals that this protein is homologous to RHL-1 throughout its length but contains one major insertion of 18 amino acids near its NH2 terminus. The COOH-terminal portion of the RHL-2/3 polypeptide has been demonstrated to contain a galactose-recognition domain by expression in an in vitro transcription/translation system. The results of these experiments indicate that RHL-1 and RHL-2/3 polypeptides are self-associated into two distinct molecules, each of which has galactose-binding activity.

Amino Acid Sequence↗
PubMed1983

Salmonella typhimurium mutants defective in UDP-D-galactose:lipopolysaccharide alpha 1,6-D-galactosyltransferase. Structural, immunochemical, and enzymologic studies of rfaB mutants.

The biochemical defect in a class of Salmonella typhimurium mutants (rfaB) defective in biosynthesis of the lipopolysaccharide core is described. Structural, immunochemical and enzymologic studies showed that: (i) the core polysaccharide completely lacked the branch alpha 1,6-D-galactosyl residue of the normal lipopolysaccharide as shown by methylation analysis and 1H nmr spectroscopy; (ii) the mutant lipopolysaccharides acted as acceptors for transfer of D-galactose from UDP-D-galactose into alpha 1,6 linkage to the proximal D-glucosyl residue of the core in a reaction catalyzed by an enzyme activity present in extracts from rfaB+ cells; (iii) the UDP-D-galactose:(glucosyl)lipopolysaccharide alpha 1,6-D-galactosyltransferase activity was absent from extracts of rfaB cells.

Carbohydrate Sequence↗
PubMed1983

On the screening for inborn errors of galactose metabolism.

The utility of a simplified diagram of procedures for screening specimens for genetic disorders in galactose metabolism is stressed. Both, early detection and institution of the dietetic treatment are imperative since these inherited disorders have clinical and pathological consequences which can be very severe in galactose-1-phosphate uridyltransferase and uridine diphosphate galactose-4-epimerase deficiencies.

Carbohydrate Epimerases↗
PubMed1983

Effects of acute carbon tetrachloride intoxication on kinetics of galactose elimination by perfused rat livers.

Seventeen livers of 200 g rats, of which seven had received 435 microliters of CCl4 (LD15) by gastric tube 36 h earlier, were isolated and perfused in a once-through system at 9 ml/min with a semi-śynthetic medium to which galactose was added to concentrations from 0.1 to 3.3 mmol/l. The relative liver weight was increased by 13% by CCl4. The portal pressure was 16 cmH2O and the oxygen consumption of the livers 20 mumol/min, both unchanged by CCl4. In each liver four to six sets of galactose elimination rate at different galactose concentrations were measured. The relation was examined by a model including modification of the simple Michaelis-Menten kinetics by allosterism. The resulting Vmax values were decreased by CCl4 from 1.20 +/- 0.18 in controls to 0.78 +/- 0.19 mumol X min-1 X 100 g-1 body weight (mean +/- SEM, P less than 0.001). The affinity constant was decreased from 0.18 +/- 0.06 to 0.11 +/- 0.02 mmol/l (mean +/- SEM, P less than 0.015) in CCl4-treated livers. The decrease in affinity constant may--if it also applies to other substances eliminated by the liver--have implications for the use of a clearance as a measure of functional capacity, since this presupposes that the affinity constant remains unchanged during liver disease.

Animals↗
PubMed1984

Dual-channel continuous-flow system for determination of phenylalanine and galactose: application to newborn screening.

We describe a dual-channel AutoAnalyzer (Technicon) system for the simultaneous measurement of phenylalanine and galactose from blood specimens on filter-paper. Using a single 1/4-in.-diameter (6-mm) specimen, we measure both components fluorometrically at a rate of 70/h. Analytical recovery with the method and the linearity of measurements vs sample concentration are excellent through the ranges of interest, 0-200 mg/L for phenylalanine and 0-800 mg/L for galactose. Carryover at the critical values during screening, 40 mg/L for phenylalanine and 100 mg/L for galactose, is essentially zero. The dual-channel system provides the means to incorporate a low-incidence test, i.e., galactosemia (incidence 1/70 000), into an existing program for phenylalanine analysis, for which the higher rates (phenylketonuria, incidence 1/11 500) easily justify the cost of mass screening.

Autoanalysis↗
PubMed1983

Reversal of galactose cataract with Sorbinil in rats.

Sorbinil, a potent aldose reductase inhibitor, can effectively block the progression of a galactose cataract even though the cataractous process is well underway. The prevention of dulcitol accumulation by Sorbinil is just as effective in reversing the cataract as the removal of galactose from the diet. The progression and reversal of the cataract were followed by ophthalmoscopy and histology. The results also further support the concept that in galactosemia the cataract is not caused by the toxic effects of galactose per se but by the consequence of the aldose reductase reaction.

Animals↗
PubMed1980

A simple assay for uridine diphosphate galactose 4-epimerase activity.

A simple fluorescent test for the activity of blood uridine diphosphate galactose 4-epimerase which converts uridine diphosphate galactose to uridine diphosphate glucose is described. The enzyme activity is visually estimated by to reduction of NAD+ (non fluorescent) to NADH (fluorescent) in a coupled reaction with uridine diphosphate glucose dehydrogenase. The appearance of fluorescence indicates that epimerase activity is present in the sample. The usefulness of this test in newborn screening programs for inborn errors of galactose metabolism is stressed.

Carbohydrate Epimerases↗
PubMed1994

Expression of the tumor marker D-galactose-beta-[1-->3]-N-acetyl-D-galactosamine by premalignant and malignant prostate.

Accurate and consistent discrimination of prostatic carcinomas from benign lesions and vice versa continues to be a vexing problem in diagnostic pathology. We have tested the usefulness of the tumor marker D-galactose-beta-[1-->3]-N-acetyl-D-galactosamine in differentiating the benign from the malignant and premalignant lesions of the prostate. A sequential galactose oxidase technique (overnight incubation), followed by Schiff's reaction (15 minutes), was done on deparaffinized tissue sections of 65 carcinomas, 25 hyperplasias, 11 foci of adenosis, and 10 normal specimens. While none of the 35 benign prostates and 11 foci of adenosis expressed D-galactose-beta-[1-->3]-N-acetyl-D-galactosamine (100% specificity), 62 (95.4% sensitivity) of 65 adenocarcinomas variably expressed the marker. We therefore propose that this simple technique may have potential use in routine histopathological analysis of prostatic specimens. This marker may also serve as the basis of assays for early detection of prostatic malignancies.

Adult↗
PubMed1994

Comparative studies on the uridine-5'-diphosphate-galactose: glycoprotein galactosyltransferase activity in rat liver and Zajdela ascitic hepatoma.

We report here data on the galactosyltransferase activity in serum, liver and Zajdela ascitic hempatoma cells and about the rate of galactose attachment to appropriate acceptors by beta(1-4, beta(1-3) and alpha(1-3) linkages in liver and hepatoma cell homogenates. It was established that in serum of Zajdela bearing rats, in host liver and in Zajdela ascitic cells, galactosyltransferase activity towards ovomucoid was elevated in comparison with control serum and liver. The activity towards low molecular acceptor (N-acetylglucosamine) in liver and hepatoma was nearly the same. The predominant isomer synthesized in both tissues was beta 1-4-galactose-N-acetylglucosamine. When asialofetuin was used as acceptor the activity of alpha(1-3) galactosyltransferase was measured. In Zajdela ascitic hepatoma cells alpha(1-3) galactosyltransferase activity was 3 times higher than that in liver. The elevated ability of the tumor cells to attach galactose residues with alpha(1-3) linkage to Gal beta 1-4GlcNAc-R sequence should be considered as a characteristic feature of these malignant cells.

Acetylglucosamine↗
PubMed1976

[Suitability of the Weidemann test for galactose in mass screening (author's transl)].

With slight practical modification, especially in the preparation of blood samples on filter paper in place of liquid blood samples, it was possible to adapt the determination of galactose dehydrogenase (Weidemann, G. (1971), this Journal 9,527) to mass screening. The technique is described, and the first results are briefly discussed and compared with those obtained over the years in our screening program with proven the Guthrie test (1): The dehydrogenase test is much quicker and shows a higher substrate specificity than the Guthrie test (duration 2 hours compared with 44 hours; false positive results of 16.87 mmol/l galactose or higher 1:42231 compared with 1:3519). It is, however, less sensitive (16.87 mmol/l compared with 1.69 mmol/l galactose), so that a combination of both tests would seem appropriate for the mass screening of new borns.

Alcohol Oxidoreductases↗
PubMed1997

Relative affinities of bovine brain 14 kDa galactose lectin binding to individual endogenous gangliosides.

Sugar-specific binding of bovine brain 14 kDa galactose-binding lectin (BBL) to individual endogenous gangliosides (GM1, GM2, GD1a, GD1b and GT1b) was studied using affinity electrophoresis of ganglioside-lectin mixture in polyacrylamide gel at pH 8.3. Unbound (free) lectin moved ahead while ganglioside-lectin complex moved very little. Sugar-specificity of binding was confirmed by reversal of the interaction by (i) presence of lactose along with the lectin and (ii) pretreatment of gangliosides with another galactose-binding lectin, Ricinus communis agglutinin. Stoichiometry of ganglioside-BBL interaction revealed that GT1b had the highest affinity for the lectin followed by GD1b and GM2, while GM1 and GD1a had the least affinity. Results indicated that a terminal sialic acid moiety covering a galactose moiety may at times enhance BBL recognition of the latter and that changes in ganglioside pattern is a possible modulator of lectin function in vivo.

Animals↗
PubMed1976

Estimation of galactose-1-phosphate in blood spotted on filter paper.

A method is described for the enzymic estimation of galactose-1-phosphate (Gal-1-P) in blood which has been applied to filter paper and allowed to dry. The successful clinical management of patients with galactosemia depends upon exclusion of galactose from their diet. Earlier studies demonstrated that red cell Gal-1-P is a sensitive indicator of exposure of such patients to galactose. These earlier methods, however, required venipuncture, preparation of washed, packed red cells, and shipment of the sample in dry ice to a central laboratory. With the present method, capillary blood can be drawn by a nonphysician, applied to filter paper and mailed in a conventional envelope at ambient temperature. From this sample, the Gal-1-P content of the red cells can be determined, if the hematocrit is known. These conveniences should allow estimates of Gal-1-P at a frequency more appropirate for optimal dietary control.

Child↗
PubMed2004

Enhanced fructose oxidase activity in a galactose oxidase variant.

Galactose oxidase (GO; EC 1.1.3.9) catalyses the oxidation of a wide range of primary alcohols including mono-, oligo- and polysaccharides. High-resolution structures have been determined for GO, but no structural information is available for the enzyme with bound substrate or inhibitor. Previously, computer-aided docking experiments have been used to develop a plausible model for interactions between GO and the D-galactose substrate. Residues implicated in such interactions include Arg330, Gln406, Phe464, Phe194 and Trp290. In the present study we describe an improved expression system for recombinant GO in the methylotrophic yeast Pichia pastoris. We use this system to express variant proteins mutated at Arg330 and Phe464 to explore the substrate binding model. We also demonstrate that the Arg330 variants display greater fructose oxidase activity than does wild-type GO.

Crystallography, X-Ray↗
PubMed2001

Characterization of a Schizosaccharomyces pombe mutant deficient in UDP-galactose transport activity.

In fission yeast, Schizosaccharomyces pombe, the carbohydrate components of the cell wall consist of galactomannan, unlike in Saccharomyces cerevisiae. We previously found that the disruption of gms1+, a gene encoding the UDP-galactose transporter required for the synthesis of galactomannan, led to the complete defect of cell surface galactosylation in Sz. pombe. The Deltagms1 strain is therefore useful for the analysis of physiological properties of galactose residues in Sz. pombe. The deletion strain of gms1+ was viable; however, itshowed an aberrant cell morphology and increased sensitivities to digestion with beta-glucanase and to various drugs, such as hygromycin B, sodium orthovanadate and Calcofluor white. A reduction of galactomannan layers of the cell wall in the Deltagms1 strain was observed by scanning and transmission electron microscopic analyses. The addition of osmotic stabilizer suppressed the morphologic defect of the Deltagms1 cells, while other phenotypes were weakly suppressed. The Deltagms1 (h90) strain was incapable of sexual conjugation during nutritional starvation. These results suggest that the cell surface galactosylation is required not only for non-sexual flocculation but also for sexual conjugation in Sz. pombe.

Biological Transport↗
PubMed1989

Modification of galactose and N-acetylgalactosamine residues by oxidation of C-6 hydroxyls to the aldehydes followed by reductive amination: model systems and antifreeze glycoproteins.

Amino acids and peptides have been attached to the C-6 hydroxyls of the galactose and the N-acetylgalactosamine by first oxidizing the C-6 hydroxyls to the aldehydes by galactose oxidase in the presence of small amounts of catalase, followed by reductive amination (alpha-amino group) in the presence of cyanoborohydride. The activity of oxidized antifreeze glycoprotein was greater than 70% of the original, and considerable activity has been retained with some substitutions on reductive amination using cyanoborohydride. The following were some activities retained (as compared with the oxidized antifreeze glycoprotein): Gly, 64; (Gly)2, 88; (Gly)3, 82; (Gly)4, 70; Gly-Gly-NH2, 44; Gly-Glu, 13; Gly-Leu, 40; Gly-Tyr, 57; Gly-Gly-Leu, 50; Gly-Gly-Phe, 30; and Gly-Gly-Val, 35. On amino acid analysis of acid hydrolysates, some release of the amino acid attached by amination occurred; e.g., Gly-Tyr gave 0.26 Gly and 0.49 Tyr per disaccharide.

Acetylgalactosamine↗