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PubMed1991

Sugar response element enhances wound response of potato proteinase inhibitor II promoter in transgenic tobacco.

The promoter region of the potato proteinase inhibitor II (PI-II) gene was studied to identify cis-acting regulatory sequences involved in sugar response using transgenic tobacco plants. The 5' control region covering an 892 nucleotide sequence upstream from the cap site and a 32 nucleotide untranslated region of the PI-II promoter was able to activate a reporter chloramphenicol acetyltransferase (cat) gene by wounding or by incubating in a sugar-free medium. This wound response was further enhanced by sugar. Hexoses, disaccharides, and some trisaccharides were strong inducers whereas pentoses, deoxy sugars, sugar acids, TCA cycle intermediates, amino acids, and other carbohydrates had little effect on the promoter activity. Deletion of the sequence between -892 and -573 abolished the wound response but not the sugar response. An additional 5' deletion to -453 removed the sugar inducibility. Locations of the cis-acting regulatory elements were further elucidated by 3' deletion analysis. Deletion of the downstream region from -520 did not affect the wound or sugar response of the promoter. However, 3' deletion mutant -574 was unable to respond to sugar but did respond weakly to wounding. Further deletion to -624 abolished both responses. Therefore, it can be concluded that a wound response element is located in between -624 and -574 and that the response is further enhanced by a sugar response element located in the sequence between -573 and -520.

Agrobacterium tumefaciens↗

PubMed1978

Dual effect of adrenalin on sugar transport in rat diaphragm muscle.

The effect of adrenalin on the membrane transport of the non-metabolized sugar, 3-methylglucose, was studied in isolated "intact" rat hemidiaphragms and related to simultaneously occurring changes in the internal levels of Na+, ATP, glucose-6-P, glycerol formation and 45Ca uptake and loss. Basal sugar transport was inhibited by low (10-8-10-5 M) concentrations of adrenalin; this was antagonized by propranolol and practolol. High concentrations (10-4-10-3 M) stimulated sugar transport, and this was blocked by propranolol and butoxamine and was dependent on external Ca2+. These results suggest interaction with two different classes of adrenergic receptors, possibly of beta 1 and beta 2 types. Both low and high concentrations increases Na+ and K+ gradients by a practolol-sensitive effect. Isoproterenol behaved identically but phenylephrine had only the two practolol-sensitive effects on sugar and ion transport. Insulin did not interfere with inhibition of sugar transport and decrease in internal Na+ but prevented stimulation of sugar transport. Under anoxia adrenalin had no effect on sugar transport but led to greater Na+ gain by tissue. Addition of 3.0 mM palmitate decreased inhibition of sugar transport without changing receptor specificity. ATP was decreased and lipolysis enchanged by high adrenalin but glucose-6-P was increased by the low concentration as well. Influx of 45 Ca was decreased by low and increased by high adrenalin; 45Ca efflux was also differentially affected. The results indicate that inhibition and stimulation of sugar transport depend on different receptors and that the latter response may override the former. The data are consistent with the earlier postulated regulatory role of sarcoplasmic Ca2+ on sugar transport in muscle, with adrenalin affecting Ca2+ fluxes and distribution both directly and indirectly.

Animals↗

PubMed1992

Differences in the enzymatic nature and the sugar-chain structure of gamma-glutamyl transferase between normal and carcinomatous human kidney and prostate.

The enzymatic and immunological nature, and the sugar chain structure, of gamma-glutamyl transferase (GGT) purified from tissues of benign prostatic hypertrophy (BPH), prostatic carcinoma (PCa) and renal cell carcinoma (RCa), were compared with those of the normal prostate (NP) and kidney (NK). The specific activities of GGTs in NP, NK, BPH, PCa and RCa were 78.9, 22.5, 105, 92.5 and 52.5 mU/mg protein, respectively. The molecular masses of GGTs from BPH, PCa and RCa were 72 kDa, 78 and 108 kDa, and 79 and 105 kDa, respectively. The Michaelis constants (Km), optimum pHs and the inhibition of GGT activities by several chemical compounds, revealed that the GGT from BPH, PCa and RCa was similar to that of normal GGT. Immunologically, the IgG fraction against anti-human seminal plasma GGT fused to the all of the GGTs tested. The sugar chain heterogeneities of the various GGTs, detected by the serial-lectin affinity technique, differed from one another. The sugar chain of GGT from BPH resembled the sugar chain from NP. On the contrary, the sugar chains of GGTs from PCa and RCa were markedly different from those from normal tissues. In the GGT from PCa, multi-antennary complex type sugar chains were more increased than the enzyme of NP. In general, as previously reported, the sugar chains of GGTs from carcinomatous tissues of prostate and kidney had an increased content of bisecting GlcNAc (beta 1-->4) containing complex type sugar chains. Moreover, the reductions of the biantennary complex type sugar chain with fucose linkage and the hybrid type sugar chain were obvious in the GGT from carcinomatous tissues of the prostate and kidney.

Adult↗

PubMed1979

Reduction in mutagenicity of cigarette smoke condensate by added sugars.

The effects of adding sugars to high- and low-tar cigarettes on the mutagenicity of their smoke condensates were studied using Salmonella typhimurium TA100 and TA98 with and without metabolic activation. The sugars tested were glucose, fructose, galactose, sorbitol, sucrose and lactose. The lowest mutagenicities observed with these sugars per mg of smoke condensate assayed on TA98 with metabolic activation were 37% (high-tar cigarettes) and 22% (low-tar cigaretts) of that of smoke condensate from untreated cigarettes. Addition of sugars increased the total amounts of smoke condensates, but the mutagenicities of the total condensates were also decreased by all the sugars, the lowest values being 35% (high-tar cigarettes) and 36% (low-tar cigarettes) of that of smoke condensates from cigarettes without added sugar. On assay with TA100 with metabolic activation, decreases in both specific and total mutangenicities of condensates of high-tar cigarettes were observed with all the sugars tested except galactose and sucrose. Treatment with glucose, fructose or sorbitol decreased the specific mutagenicity of condensates of low-tar cigarettes and glucose and fructose reduced also their total mutagenicity. The effects of added sugars were more marked when assayed on TA98 than on TA100 and of the sugars tested fructose and sorbitol had the greatest effects. Addition of sugars had no effect of the mutagenicity of cigarette-smoke condensate without metabolic activation.

Carbohydrates↗

PubMed1992

Stripping interfering sugars from samples using adapted bacteria.

Bacteria adapted to individual sugars quickly remove targeted sugars--stripping them--from samples in which unwanted sugars interfere. Adapted bacteria are equivalent to specific reagents for removal of sugars down to bacterial Km values, micromolar to submicromolar concentrations. Bacterial stripping is a simple method, useful when background sugars in micro-to millimolar concentrations (or larger) interfere with analysis of sought-for sugars. Bacteria such as Escherichia coli and Klebsiella are easily adapted to individual sugars such as lactose, fructose, etc., by growing the bacteria on them. Hence one can easily create (and store) many kinds of cells ready to sponge up or strip out unwanted compounds. E. coli specifically remove several sugars from samples containing 100-500 nmol of sugars, using 1-5 mg of adapted cells, and 25 degrees C temperatures. Stripping requires 1-5 min and consists of mixing cells and sample, spinning down the cells, and withdrawal of stripped supernate. A 1-5 min interval is adequate for uptake and stripping, but far too short for cells to metabolize the sugars that were taken up. Hence the cells do not leak metabolites, but act as specific adsorbants without injection of appreciable byproducts into the sample.

Adaptation, Biological↗

PubMed1994

Effect of high-sugar intake by low-income pregnant adolescents on infant birth weight.

PURPOSE: The objective of this study was to determine the effect of total sugar intake by pregnant adolescents from low-income families on infant birth weight and small-for-gestational-age (SGA) infants. METHODS: The study sample consisted of 337 adolescents, enrolled in a county-wide demonstration project in Camden, New Jersey, who delivered live, singleton newborns. The adolescents were divided into two groups at the 90th percentile for the study sample total sugar intake (206 g): high-sugar intake (> or = 206 g, n = 34) and low-sugar intake group (< 206 g, n = 303). RESULTS: The sample was 46% black, 30% white, and 24% Hispanic. The sample gestational age and birth weight (mean +/- SD) were 39 +/- 3 weeks and 3189 +/- 666 g, respectively. After adjusting for energy intake, the high- compared with the low-sugar intake group was more likely to consume higher total sugar and carbohydrate but lower protein and fat. Likewise, the high-compared to the low-sugar intake group consumed significantly more calcium and magnesium. After adjusting for possible confounding variables such as maternal age, ethnicity, marital status, parity, smoking, net weight gain, body mass index, energy intake, and gestational age at birth, adolescents on high- compared to low-sugar diets gave birth to infants weighing 215 +/- 104 g less (p = 0.04). The adjusted odds ratios were 3.41 (95% confidence interval, 1.14 to 10.23) for delivering a SGA infant among adolescents with high- compared with low-sugar intakes. CONCLUSIONS: Low-income adolescents consuming high-sugar diets are at increased risk for delivering lower birth weight and SGA infants.

Adolescent↗

PubMed1986

Sugar conjugates of pyridinium aldoximes as antidotes against organophosphate poisoning.

A series of pyridinium aldoximes having a sugar conjugated to the pyridine ring has been prepared as potential antidotes against organophosphate poisoning. The sugar residue was attached either directly through C-1 or C-6 of the pyranose ring or through a C3 bridge between the glycosyl group and the nitrogen atom of the pyridine moiety. Attachment of a sugar group to the oxime derivative seems to increase the bioavailability of the antidote. The clearance rate of the sugar conjugates was significantly lower than that of their non-sugar analogs and thus they were retained longer in the blood circulation. The sugar derivatives were more potent in decreasing paraoxon-induced hypothermia (which is regulated within the central nervous system) than N-methyl-2-pyridiniumaldoxime methanesulfonate, one of the most commonly used mono-oximes. The sugar analogs were also less toxic than the non-sugar analogs; some also displayed higher efficacy. The mechanism underlying the improved features of the sugar oximes, and the structural requirements in relation to the sugar attachment to the oxime function, are discussed.

Animals↗

PubMed1999

Assessment of advice to reduce dietary fat and non-milk extrinsic sugar in a free-living male population.

OBJECTIVE: To compare the effect of advice to reduce both dietary fat and sugar with advice to reduce fat alone on subsequent dietary intake in Scottish men. DESIGN: A parallel design intervention study was employed to measure compliance to the two types of dietary advice. Subjects were randomly assigned to Group 1 (advice to reduce fat and non-milk extrinsic (NME) sugar), Group 2 (advice to reduce fat only, ad libitum sugar) or a control Group 0 (no advice). Compliance was assessed by two 4-day food diaries over 6 months. SETTING: The study was conducted in the Strathclyde area of Scotland. SUBJECTS: Subjects were normal to moderately overweight Scottish men. The men recruited were non-dieting and volunteered for a 'healthy eating' study with the aim to improve the 'healthiness' of their diet. RESULTS: Groups 1 and 2 achieved the dietary target for fat, reducing their mean intake to below 35% energy. Group 1 achieved a statistically significant reduction in percentage energy from NME sugar in the short term (6 weeks), decreasing their mean intake from 9.9% to 7.2% energy. This initial decrease appeared to slip back towards baseline levels at 6 months (8.1% energy from NME sugar) and was no longer significantly different from baseline. At 6 months Group 1 reported a significantly lower mean energy intake than at baseline, whereas Group 2 adjusted for an initial decrease in energy intake and by 6 months energy intakes were not significantly different from baseline intakes. Group 2 appeared to compensate for the absolute reduction in dietary fat with a slight increase in total sugars and the maintenance of NME sugar intakes. CONCLUSIONS: Subjects in Group 1 complied with advice to reduce both fat and sugar over 6 weeks but to a lesser extent over 6 months. The 1.8% reduction in percentage energy from NME sugars in Group 1 at 6 months may not have reached significance due to the small sample size. Alternatively it may be that free-living populations find it hard to maintain concurrent reductions in fat and sugar owing to the well-documented inverse relationship between intakes of these macronutrients when expressed as a proportion of energy.

Adult↗

PubMed1991

Cytochalasin B interferes with conformational changes of the human erythrocyte glucose transporter induced by internal and external sugar binding.

To gain insight into the mechanism of facilitated sugar transport and possible mechanisms by which glucose transporter intrinsic activity might be altered, we have investigated conformational changes of the human erythrocyte glucose transporter induced by internal and external sugar binding and by the transporter inhibitor, cytochalasin B. Changes in the ability of thermolysin to digest glucose transporters present in erythrocyte ghosts were used to monitor conformational changes of the glucose transporter. The degree of protease digestion was determined by the amount of undigested glucose transporter remaining after the protease treatment, as assessed in Western blots using the glucose transporter specific monoclonal antibody 7F7.5. D-Glucose, the physiological substrate of the transporter, increased the transporter's susceptibility to cleavage by thermolysin. Nontransportable glucose analogues which bind specifically to either an internal or external glucose transporter sugar binding site also altered susceptibility of the transporter to thermolysin. Both methyl and propyl glucoside, which preferentially bind the internal sugar site, increased thermolysin susceptibility of the glucose transporter in a manner similar to that of D-glucose. In contrast, 4,6-O-ethylideneglucose, which preferentially binds the external sugar site, protected the transporter from thermolysin digestion. These results suggest that sugar binding to internal and external sugar sites induces distinct conformational changes and that the observed D-glucose effect on the susceptibility of the glucose transporter to thermolysin is due to D-glucose at equilibrium predominantly forming a complex with the internal sugar site. The protection from cleavage by thermolysin caused by external sugar binding is attenuated by the addition of an internally binding sugar.(ABSTRACT TRUNCATED AT 250 WORDS)

Biological Transport↗

PubMed2001

Evidence for the involvement of Ala 166 in coupling Na(+) to sugar transport through the human Na(+)/glucose cotransporter.

We mutated residue 166, located in the putative Na(+) transport pathway between transmembrane segments 4 and 5 of human Na(+)/glucose cotransporter (hSGLT1), from alanine to cysteine (A166C). A166C was expressed in Xenopus laevis oocytes, and electrophysiological methods were used to assay function. The affinity for Na(+) was unchanged compared to that of hSGLT1, whereas the sugar affinity was reduced and sugar specificity was altered. There was a reduction in the turnover rate of the transporter, and in contrast to that of hSGLT1, the turnover rate depended on the sugar molecule. Exposure of A166C to MTSEA and MTSET, but not MTSES, abolished sugar transport. Accessibility of A166C to alkylating reagents was independent of protein conformation, indicating that the residue is always accessible from the extracellular surface. Sugar and phlorizin did not protect the residue from being alkylated, suggesting that residue 166 is not located in the sugar pathway. MTSEA, MTSET, and MTSES all changed the pre-steady-state kinetics of A166C, independent of pH, and sugars altered these kinetics. The inability of MTSEA-labeled A166C to transport sugar was reversed (with no major change in Na(+) and sugar affinity) if the positive charge on MTSEA was neutralized by increasing the external pH to 9.0. These studies suggest that the residue at position 166 is involved in the interaction between the Na(+) and sugar transport pathways.

Alanine↗

PubMed2001

The red blood cell glucose transporter presents multiple, nucleotide-sensitive sugar exit sites.

At any instant, the human erythrocyte sugar transporter presents at least one sugar export site but multiple sugar import sites. The present study asks whether the transporter also presents more than one sugar exit site. We approached this question by analysis of binding of [3H]cytochalasin B (an export conformer ligand) to the human erythrocyte sugar transporter and by analysis of cytochalasin B modulation of human red blood cell sugar uptake. Phloretin-inhibitable cytochalasin B binding to human red blood cells, to human red blood cell integral membrane proteins, and to purified human red blood cell glucose transport protein (GluT1) displays positive cooperativity at very low cytochalasin B levels. Cooperativity between sites and K(d(app)) for cytochalasin B binding are reduced in the presence of intracellular ATP. Red cell sugar uptake at subsaturating sugar levels is inhibited by high concentrations of cytochalasin B but is stimulated by lower (<20 nM) concentrations. Increasing concentrations of the e1 ligand forskolin also first stimulate then inhibit sugar uptake. Cytochalasin D (a cytochalasin B analogue that does not interact with GluT1) is without effect on sugar transport over the same concentration range. Cytochalasin B and ATP binding are synergistic. ATP (but not AMP) enhances [3H]cytochalasin B photoincorporation into GluT1 while cytochalasin B (but not cytochalasin D) enhances [gamma-32P]azidoATP photoincorporation into GluT1. We propose that the red blood cell glucose transporter is a cooperative tetramer of GluT1 proteins in which each protein presents a translocation pathway that alternates between uptake (e2) and export (e1) states but where, at any instant, two subunits must present uptake (e2) and two subunits must present exit (e1) states.

3-O-Methylglucose↗

PubMed1999

Pharmacists' knowledge, attitudes and practices concerning sugar-free medicines.

AIMS: To examine the attitudes of pharmacists to sugar in medicine and sugar-free preparations and their levels of knowledge concerning sugar-free preparations and the implications for dental health. DESIGN: A questionnaire was designed with a mixture of closed and open-ended questions. SETTING: Pharmacists practising in the Greater Belfast area of Northern Ireland. METHOD: Seventy pharmacists were randomly chosen from the list of pharmacists practising in the area and were asked to participate in the study. RESULTS: Responses were obtained from 52 of the 70 selected pharmacists, representing a response rate of 74%. Seventy-five per cent of the pharmacists stated that they had not received formal education concerning sugar in medication and it's effect on dental health. Their main source of information on the subject was dental health literature. Eighty-seven per cent felt that all medication should be available in sugar-free form. Forty-six per cent stated that sugar in medication was definitely an important cause of dental caries in children and 44% felt that it was a possible factor. The major factors influencing the provision of sugar-free medicines were parental request, health promotion literature, reports and media advertising. Thirty-nine per cent of the pharmacists always offered a sugar-free preparation for over-the-counter medication (provided that a sugar-free alternative was available), and 56% sometimes did so. Fifty per cent always offered a sugar-free form for prescribed items wherever possible, the remainder depended on it being specified by the prescriber. CONCLUSION: There is a high level of interest in this issue among pharmacists, but there is a need for an increased educational input on a continuous basis.

Attitude of Health Personnel↗

PubMed1985

Some nutritional properties of unrefined sugar and its promotion of the survival of new-born rats.

1. The claims that rats fed on diets with 'brown sugar' (unrefined muscovado) perform better in a number of ways than do rats fed on refined white sugar (sucrose) have been examined. 2. Male Wistar rats were fed on purified diets from weaning, in which the carbohydrate component was either maize starch or unrefined sugar or sucrose. The sugars produced no differences in growth rate, body composition, or the weights of liver or kidneys. Compared with sucrose, unrefined sugar produced an increase in blood cholesterol and in the activity of hepatic fatty acid synthetase, and a greater increase in blood triglyceride. In confirmation of earlier results, rats fed on either sugar had heavier livers and kidneys, increased activity of hepatic glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and a higher concentration of plasma triglyceride compared with rats fed on maize starch. 3. Female Sprague-Dawley rats were fed on the same three diets as the male rats, and mated when they weighed about 200 g. No difference was seen in their ability to mate, the progress of pregnancies, or the sizes of the litters. Does fed on unrefined sugar produced litters of higher viability than did does fed on starch or sucrose. Survival was between 85 and 100% with unrefined sugar and between 30 and 75% with starch or sucrose. 4. Unrefined muscovado sugar has thus been shown to contain a factor required by female rats for the proper viability of their pups. This may be the same 'Reproductive Factor R' as that described by Wiesner & Yudkin (1951). In certain circumstances, unrefined muscovado sugar might therefore contribute to the nutritional value of a human diet, although in what circumstances, in what respect and to what extent it might do so, is by no means clear.

Animal Nutritional Physiological Phenomena↗

PubMed2004

High intake of added sugar among Norwegian children and adolescents.

OBJECTIVE: It is debated whether the intake of added sugar displaces micronutrient-rich foods and dilutes the nutrient density of the diet, and whether there is a link between sugar and the increased rate of obesity. The objectives of this study were to examine the effect of added sugar on the intakes of energy, micronutrients, fruit and vegetables, and to examine the association between intake of added sugar and age, sex, body mass index, physical activity, inactivity and parents' education. DESIGN: Participants recorded their food intake in pre-coded food diaries for 4 days and filled in a questionnaire about physical activity, watching television (TV)/using a personal computer (PC) and parents' education. SUBJECTS: Three hundred and ninety-one 4-year-olds, 810 students in the 4th grade (9 years old) and 1005 in the 8th grade (13 years old) were included in the study. RESULTS: The intakes of all nutrients, except alpha-tocopherol among 4-year-olds and vitamin C among 4-year-olds and 4th graders, decreased with increasing content of added sugar in the diet. Moreover, high consumers of added sugar had a 30-40% lower intake of fruit and vegetables than did low consumers. A negative association was observed between consumption of added sugar and body mass index among girls in the 8th grade (P=0.013), whereas a positive association was observed among 4-year-old boys (P=0.055). Associations between physical activity, hours spent watching TV/using a PC, parents' education and the energy intake from added sugar varied in the different age groups. CONCLUSIONS: This study showed a negative association between the intake of added sugar and intakes of micronutrients, fruit and vegetables. The negative association between sugar intake and intake of fruit and vegetables is important from a public health perspective, since one of the main health messages today is to increase current intake of fruit and vegetables.

Adolescent↗

PubMedDate not supplied

Apparent absorption efficiencies of nectar sugars in the Cape sugarbird, with a comparison of methods.

Nectarivore sugar preferences and nectar composition in the Cape Floristic Kingdom (southern Africa) differ from trends reported for analogous systems in America and Europe in that sugarbirds and sunbirds show no aversion to sucrose, which is the dominant nectar sugar in many of their food plants. To elucidate the physiological bases (if any) of nectarivore sugar preferences, we determined apparent sugar absorption efficiencies in a passerine endemic to this region, the Cape sugarbird Promerops cafer. Apparent absorption efficiencies for the three major nectar sugars, sucrose, glucose, and fructose, were extremely high (> 99%), as in other specialized avian nectarivores. Xylose, a pentose sugar recently reported in the nectar of some Proteaceae, was absorbed and/or metabolized inefficiently, with a mean of 47.1% of ingested sugar recovered in cloacal fluid. We did not measure the proportions of xylose that were absorbed and/or metabolized. We also compared three methods of estimating absorption efficiency: (1) measurements of total sugar in cloacal fluid with refractometry, without correction for differences between volumes of ingesta and excreta; (2) the same measurements combined with correction for volume differences; and (3) HPLC analyses quantifying individual sugars in cloacal fluid, with correction for volume differences. Refractometry has been frequently used in previous studies. For all sugars except xylose, method 1 yielded results similar to those obtained with method 2, but the convergence was artifactual, and we do not recommend use of this method. Apparent absorption efficiencies calculated with method 2 underestimated true absorption efficiency, because refractometry measures nonsugar solutes, but this error is biologically significant only when efficiencies are low.

Absorption↗

PubMed2000

An investigation of the water-binding properties of protein + sugar systems.

The water-binding properties of sucrose + beta-lactoglobulin and trehalose + beta-lactoglobulin prepared by freeze-drying, spray-drying and evaporation from solution have been studied using gravimetric methods. The hydration characteristics of the individual sugars are dependent on the method of drying, and different isotherms have been recorded for each of the sample preparations. However, the initial hydration isotherms produced for the sugar + protein samples appear to be very similar for each sample type irrespective of drying method, with the sugar present in the amorphous glassy form in all cases. There is evidence of interaction between the sugar in this form and protein, specifically in the hydration region where single hydrogen-bonded water is expected to be bound. The magnitude of the interaction appears to be of the same order for both sugars. Irrespective of the method of preparation, rehydration of the sugar + protein complexes above a critical value causes a transition resulting in the sugar adopting a crystalline form and phase separation of the sugar and protein. In this crystalline form there is no evidence of interaction between the sugar and protein. For sugar + protein samples prepared by evaporation from solution, a small amount (approximately 3% by weight) of water is trapped in the complex even under extreme conditions of dehydration.

Animals↗

PubMed1999

beta1-4Galactosyltransferase activity of mouse brain as revealed by analysis of brain-specific complex-type N-linked sugar chains.

We previously reported two brain-specific agalactobiantennary N-linked sugar chains with bisecting GlcNAc and alpha1-6Fuc residues, (GlcNAcbeta1-2)(0)(or)(1)Manalpha1-3(GlcNAcbeta1-2M analpha1-6)(GlcNA cbeta1-4)Manbeta1-4GlcNAcbeta1-4(Fucalpha1-6)Glc NAc [Shimizu, H., Ochiai, K., Ikenaka, K., Mikoshiba, K., and Hase, S. (1993) J. Biochem. 114, 334-338]. Here, the reason for the absence of Gal on the sugar chains was analyzed through the detection of other complex type sugar chains. Analysis of N-linked sugar chains revealed the absence of Sia-Gal and Gal on the GlcNAc residues of brain-specific agalactobiantennary N-linked sugar chains. We therefore investigated the substrate specificity of galactosyltransferase activities in brain using pyridylamino derivatives of agalactobiantennary sugar chains with structural variations in the bisecting GlcNAc and alpha1-6Fuc residues as acceptor substrates. While the beta1-4galactosyltransferases in liver and kidney could utilize all four oligosaccharides as substrates, the beta1-4galactosyltransferase(s) in brain could not utilize the agalactobiantennary sugar chain with both bisecting GlcNAc and Fuc residues, but could utilize the other three acceptors. Similar results were obtained using glycopeptides with agalactobiantennary sugar chains and bisecting GlcNAc and alpha1-6Fuc residues as substrates. The beta1-4galactosyltransferase activity of adult mouse brain thus appears to be responsible for producing the brain-specific sugar chains and to be different from beta1-4galactosyltransferase-I. The agalactobiantennary sugar chain with bisecting GlcNAc and alpha1-6Fuc residues acts as an inhibitor against "brain type" beta1-4galactosyltransferase with a K(i) value of 0.29 mM.

Animals↗

PubMed1988

Structures of sugar chains of a p-nitrophenyl acetate-hydrolyzing esterase from the microsomes of rat liver.

The structures of sugar chains of a p-nitrophenyl acetate-hydrolyzing esterase from the microsomes of rat liver were established. The enzyme contained mannose and glucosamine as sugar components. Asparagine-linked sugar chains of the esterase were liberated by hydrazinolysis. After N-acetylation of the hydrazinolysate, the reducing ends of the sugar chains were coupled with 2-aminopyridine. Fluorescent pyridylamino (PA-) derivatives of sugar chains thus obtained were purified by gel filtration and reversed-phase HPLC. Eleven PA-sugar chains were obtained. The structures of the PA-sugar chains were first identified by HPLC using two series of separation systems by which 11 PA-oligomannose-type sugar chains with known structures could be separated. Further elucidation of the structures of each PA-sugar chain was performed by exoglycosidase digestions and partial acetolysis. The structures of two of the PA-sugar chains were further confirmed by 500 mHz 1H-NMR spectroscopy.

Animals↗