Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.1.18 (branching enzyme)
 628 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

During the investigation of the histochemical synthesis of glycogen particles from glucose 1-phosphate by the phosphorylase-branching glycosyltransferase system in various tissue cells, it was observed that focal synthesis localized in a certain area of the cytoplasm occurred in some cells. This differed from the usual synthesis in which particles of similar size were synthesized within the cytoplasm. Otherwise, cytoplasmic particles of various size were also synthesized in other cells under the same histochemical condition. The possible significance of the presence of these patterns in glycogen synthesis is discussed.
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PMID:Intracellular localization and size of glycogen particles in glycogen synthesized under histochemical conditions. 17 57

Electron histochemical techniques for glycogen synthetase has been applied to the living retina of the chick and the polyglucose particles synthesized from UDPG in the paraboloid of the accessory cone were compared with those synthesized by the conventional histochemical techniques. In the retina incubated in the medium for glycogen synthetase in vivo, synthesized polyglucose particles were located in the cytoplasmic matrices and most of the particles were less than 200 A in diameter. These particles were rather well stainable with lead citrate and filled the cytoplasmic matrices. However, the tubular structures were not flattened, but slightly dilated. Compared with polyglucose particles synthesized in vitro by glycogen synthetase, those demonstrated by the in vivo histochemical techniques showed closer resemblance to native glycogen particles in size and stainability with lead citrate. The polyglucose particles synthesized from UDPG by glycogen synthetase were apparently different from those synthesized from glucose-1-phosphate by phosphorylase and branching glycosyltransferase.
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PMID:Polyglucose particles histochemically synthesized by glycogen synthetase activity in the living chick retina. 82 86

Ultrastructural and histochemical studies on human gastric cancer cells disclosed the presence of native and synthesized glycogen particles. The glycogen particles were investigated in the histochemical synthesis of glycogen particles from glucose 1-phosphate by the phosphorylase-branching glycosyltransferase system and non-incubated native glycogen in human gastric adenocarcinoma tubulare. It was observed that focal synthesis localized inthe intracytoplasmic matrix and intranucleus. Intranuclear synthesized glycogen appeared as a rosette form ranging from 1100 to 1300 A in diameter and free particles ranging from 325 to 900 A in diagmeter. The synthesis of glycogen appeared in the nucleus as well as in the cytoplasm of the human gastric cancer cells, and the synthesized glycogen was observed as a group of particles. Newly formed glycogen particles appeared occasionally in the interchromatin area as a large macromolecular structure of rosette form. Native glycogen appeared as a free-particle (250-333 A, medium =300 A) and aggregated rosette from (694-1050 A, medium=917 A) in the autophagosome of gastric cancer cells. There was not, however, a native glycogen particle in the nuclei of gastric cancer cells. Under certain conditons the nuclei of gastric cancer cells can acquire the capacity to synthesize glycogen.
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PMID:Intranuclear synthesized and native glycogen particles in human gastric cancer: ultrastructure and histochemistry. 83 12

A correlation between increased beta-1,6 branching of N-linked carbohydrates and the ability of a cell to metastasize or to form a tumor has been observed in several experimental models. Lec9 Chinese hamster ovary (CHO) mutants exhibit a drastic reduction in tumorigenicity in nude mice, and this phenotype directly correlates with their ability to attach an increased proportion of beta-1,6-branched carbohydrates to the G glycoprotein of vesicular stomatitis virus (J. Ripka, S. Shin, and P. Stanley, Mol. Cell. Biol. 6:1268-1275, 1986). In this paper we provide evidence that cellular carbohydrates from Lec9 cells also contain an increased proportion of beta-1,6-branched carbohydrates, although they do not possess significantly increased activity of the beta-1,6 branching enzyme (GlcNAc-transferase V). Biosynthetic labeling experiments show that a substantial degree of underglycosylation occurs in Lec9 cells and that this affects several classes of glycoproteins. Lec9 cells synthesize ca. 40-fold less Glc3Man9GlcNAc2-P-P-lipid and ca. 2-fold less Man5GlcNAc2-P-P-lipid than parental cells do. In addition, Lec9 cells possess ca. fivefold less protein-bound oligosaccharide intermediates, and one major species is resistant to release by endo-beta-N-acetylglucosaminidase H (endo H). Membranes of Lec9 cells exhibit normal mannosylphosphoryldolichol synthase, glucosylphosphoryldolichol synthase, and N-acetylglucosaminylphosphate transferase activities in the presence of exogenous dolichyl phosphate. However, in the absence of exogenous dolichyl phosphate, mannosylphosphoryldolichol synthase and glucosylphosphoryldolichol synthase activities are reduced in membranes of Lec9 cells, indicating that membranes of Lec9 cells are deficient in lipid phosphate. This was confirmed by analysis of lipids labeled by [3H]mevalonate, which showed that Lec9 cells have less lipid phosphate than parental CHO cells. Mechanisms by which a defect in the synthesis of dolichol-oligosaccharides might alter the degree of beta-1,6 branching in N-linked carbohydrates are discussed.
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PMID:Control of carbohydrate processing: increased beta-1,6 branching in N-linked carbohydrates of Lec9 CHO mutants appears to arise from a defect in oligosaccharide-dolichol biosynthesis. 272 6

A mutant strain of Escherichia coli K-12, designated 618, accumulates glycogen at a faster rate than wild-type strain 356. The mutation affects the ADPglucose pyrophosphorylase regulatory properties (N. Creuzat-Sigal, M. Latil-Damotte, J. Cattaneo, and J. Puig, p. 647-680, in R. Piras and H. G. Pontis, ed., Biochemistry of the Glycocide Linkage, 1972). The enzyme is less dependent on the activator, fructose 1,6 bis-phosphate for activity and is less sensitive to inhibition by the inhibitor, 5'-AMP. The structural gene, glgC, for this allosteric mutant enzyme was cloned into the bacterial plasmid pBR322 by inserting the chromosomal DNA at the PstI site. The glycogen biosynthetic genes were selected by cotransformation of the neighboring asd gene into an E. coli mutant also defective in branching enzyme (glgB) activity. Two recombinant plasmids, pEBL1 and pEBL3, that had PstI chromosomal DNA inserts containing glgC and glgB were isolated. Branching enzyme and ADPglucose pyrophosphorylase activities were increased 240- and 40-fold, respectively, in the asd glgB mutant, E. coli K-12 6281. The E. coli K-12 618 mutant glgC gene product was characterized after transformation of an E. coli B ADPglucose pyrophosphorylase mutant with the recombinant plasmid pEBL3. The kinetic properties of the cloned ADPglucose pyrophosphorylase were similar to those of the E. coli K-12 618 enzyme. The inserted DNA in pEBL1 was arranged in opposite orientation to that in pEBL3.
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PMID:Cloning and expression of the Escherichia coli glgC gene from a mutant containing an ADPglucose pyrophosphorylase with altered allosteric properties. 301 41

The mechanism of action of liver branching enzyme has been studied by using as substrate two polysaccharides in which the non-reducing ends had been labelled by incubation with phosphorylase and a trace amount of [(14)C]glucose 1-phosphate. After these polysaccharides had been treated with branching enzyme, their structure was analysed by periodate oxidation, by degradation with phosphorylase and amylo-(1-->6)-glucosidase and by degradation with pullulanase. All the results indicate that the branching enzyme catalyses the transfer from (1-->4)- to (1-->6)-linkage of a chain of glucose units, the minimum length of which is six glucose units. A maltodextrin containing 16 glucose units was not acted on by the branching enzyme.
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PMID:A study of the reaction catalysed by the liver branching enzyme. 429 May 51

Polyglucose particles histochemically synthesized from glucose 1-phosphate by phosphorylase and branching glycosyltransferase were observed in the gastric carcinoma cells, in intestinal metaplastic epithelium of the gastric mucosa and in fetal epithelium of the fetal gastric mucosa by light and electron microscopical studies. Light microscopical observations resembled those in previous reports. As for the electron microscopical observations, in gastric carcinoma cells, the polyglucaose synthesizing area were expansively widened by a deposition of synthesized polyglucose particles. Three patterns of their intracellular distribution, (Focal type, scattered type and singly deposited type) were observed. Besides, two types of polyglucose particle were synthesized. One type appeared as monoparticles which were relatively similar in size and the other type appeared as rosette-like structures which varied in size. Larger polyglucose particles which resembled the polyglucose particle synthesized in the fetal epithelium were observed among them. In the intestinal metaplastic epithelium, polyglucose particles which were similar in size were synthesized in narrow focal areas of the cytoplasmic matrix. The distribution, shape and size of polyglucose particles synthesized in the carcinoma cells were irregular as compared with those in the intestinal metaplastic elpithelium. It seems that these irregularities were due to the influence of enzymne deviation caused by carcinoma.
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PMID:Histochemical observations of polyglucose synthesized by enzyme activities in human gastric carcinoma. 644 38

Three forms of starch branching enzyme (BE) from developing hexaploid wheat (Triticum aestivum) endosperm have been partially purified and characterized. Immunological cross-reactivities indicate that two forms (WBE-IAD, 88 kD, and WBE-IB, 87 kD) are related to the maize BE I class and that WBE-II (88 kD) is related to maize BE II. Comparison of the N-terminal sequences from WBE-IAD and WBE-II with maize and rice BEs confirms these relationships. Evidence is presented from the analysis of nullisomic-tetrasomic wheat lines demonstrating that WBE-IB is located on chromosome 7B and that the WBE-IAD fraction contains polypeptides that are encoded on chromosomes 7A and 7D. The wheat endosperm BE classes are differentially expressed during endosperm development. WBE-II is expressed at a constant level throughout mid and late endosperm development. In contrast, WBE-IAD and WBE-IB are preferentially expressed in late endosperm development. Differences are also observed in the kinetic characteristics of the enzymes. The WBE-I isoforms have a 2- to 5-fold higher affinity for amylose than does WBE-II, and the WBE-I isoforms are activated up to 5-fold by phosphorylated intermediates and inorganic phosphate, whereas WBE-II is activated only 50%. The potential implications of this activation of BE I for starch biosynthesis are discussed.
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PMID:Differential expression and properties of starch branching enzyme isoforms in developing wheat endosperm. 900 95

The enzymatic reactions of bacterial glycogen and plant starch synthesis are similar and some of the properties of the biosynthetic enzymes are compared. Regulation occurs at the synthesis of ADPglucose and in almost all cases, ADPglucose pyrophosphorylase, is allosterically activated about 10- to over 40-fold by glycolytic intermediates and inhibited by AMP, ADP or Pi. The activator specificity of the ADPglucose pyrophosphorylase varies with respect to the source of enzyme and can be correlated to the major assimilation pathway occurring in the organism. For example, ADPglucose pyrophosphorylases from plants and other oxygenic photosynthetic organisms are activated by 3-phosphoglycerate. Organisms using glycolysis for carbon assimilation have ADPglucose pyrophosphorylases with fructose-1,6-bis-phosphate as the major activator. Chemical modification and site-directed mutagenesis studies that have determined the activator binding sites for some enzymes are described. The structural genes of Escherichia coli ADPglucose pyrophosphorylase allosteric mutants which no longer require activator for activity have been isolated. Transformation of plant systems with an allosteric bacterial mutant gene (but not with the wild-type gene) increases their starch content. Transformed potato tubers can have 25-60% more starch than the normal tuber indicating the importance of allosteric regulation of ADPglucose synthesis. The increase of a normal plant product by transformation of the plant with a gene encoding the rate-limiting enzyme in starch synthesis is an important biotechnological advance and suggests the possibilities of changing starch composition (extent of branching and chain sizes) via transformation with the starch synthase and branching enzyme genes.
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PMID:ADPglucose pyrophosphorylase: basic science and applications in biotechnology. 970 99

The molecular mechanisms regulating hemicelluloses and pectin biosynthesis are poorly understood. An important question in this regard is how glycosyltransferases are oriented in the Golgi cisternae, and how nucleotide sugars are made available for the synthesis of the polymers. Here we show that the branching enzyme xyloglucan alpha,1-2 fucosyltransferase (XG-FucTase) from growing pea (Pisum sativum) epicotyls was latent and protected against proteolytic inactivation on intact, right-side-in pea stem Golgi vesicles. Moreover, much of the XG-FucTase activity was membrane associated. These data indicate that XG-FucTase is a membrane-bound luminal enzyme. GDP-Fuc uptake studies demonstrated that GDP-Fuc was taken up into Golgi vesicles in a protein-mediated process, and that this uptake was not competed by UDP-Glc, suggesting that a specific GDP-Fuc transporter is involved in xyloglucan biosynthesis. Once in the lumen, Fuc was transferred onto endogenous acceptors, including xyloglucan. GDPase activity was detected in the lumen of the vesicles, suggesting than the GDP produced upon transfer of Fuc was hydrolyzed to GMP and inorganic phosphate. We suggest than the GDP-Fuc transporter and GDPase may be regulators of xyloglucan fucosylation in the Golgi apparatus from pea epicotyls.
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PMID:GDP-fucose uptake into the Golgi apparatus during xyloglucan biosynthesis requires the activity of a transporter-like protein other than the UDP-glucose transporter. 1071 51


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