Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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)

Using a cDNA library prepared from poly(A)+ RNA from 10-day-old rice endosperm, partial nucleotide sequences of randomly isolated clones were analyzed. A total of 153 (30.6%) out of 500 cDNA clones showed high amino acid identity to previously identified genes. There was significant redundancy in cDNAs encoding prolamine and glutelin. About 21.0% of the cDNA clones were found to code for seed storage protein genes. Consequently, 37 independent genes were identified. Using cDNA clones encoding glutelin, prolamine, seed allergen, alpha-1,4-glucan branching enzyme, glycine-rich RNA binding protein, metallothionein, non-specific lipid-transfer protein and ubiquitin conjugating enzyme the accumulation of mRNA during rice seed development was compared. Genes associated with seed storage protein and starch biosynthesis were expressed according to expected developmental stages. Glycine-rich RNA binding protein genes as well as metallothionein-like protein genes were highly expressed in developing seeds, but low in leaves of whole plants.
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PMID:Analysis of randomly isolated cDNAs from developing endosperm of rice (Oryza sativa L.): evaluation of expressed sequence tags, and expression levels of mRNAs. 854 95

In the overtly differentiated colonies of Streptomyces coelicolor A3(2), discrete phases of glycogen synthesis are found at the vegetative/aerial mycelium boundary (phase I) and in the immature spore chains at aerial hyphal tips (phase II). We have characterized two S. coelicolor glgB genes encoding glycogen branching enzyme, which are well separated in the genome. Disruption of glgBl led to the formation of abnormal polyglucan deposits at phase I, with phase II remaining normal, whereas disruption of glgBII interfered specifically with phase II deposits, and not with those of phase I. Thus, each branching enzyme isoform is involved in a different phase of glycogen synthesis. This situation contrasts with that in simple bacteria, which typically have a single set of enzymes for glycogen metabolism, and more closely resembles that in plants.
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PMID:Tissue-specific glycogen branching isoenzymes in a multicellular prokaryote, Streptomyces coelicolor A3(2). 859 63

The action of branching enzyme (EC 2.4.l.l8) from Bacillus stearothermophilus on amylose was analyzed. The enzyme reduced the molecular size of amylose without increasing the reducing power. This result could not be explained by the normal branching reaction model. When the product was treated with glucoamylase (an exo++-type amylase), a resistant component remained. The glucoamylase-resistant component was easily digested by an endo-type alpha-amylase or by isoamylase plus glucoamylase. These results suggested that the glucoamylase-resistant component was a cyclic glucan composed of alpha-1,4- and alpha-l,6-glucosidic linkages. In other words, it was suggested that branching enzyme catalyzed cyclization of the alpha-l,4-glucan chain of the amylose molecule to form an alpha-l,6-glucosidic linkage, thereby forming two smaller molecules. Mass spectrometry also supported the cyclic nature of the product.
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PMID:Cyclization reaction catalyzed by branching enzyme. 862 87

Consistent with previous results, overexpression of rabbit skeletal muscle glycogen synthase in COS cells did not lead to overaccumulation of glycogen unless activating Ser-->Ala mutations were present at key regulatory phosphorylation sites 2 (Ser7) and 3a (Ser644) in the enzyme. In addition, we found that expression of glycogenin, glycogen branching enzyme, or UDP-glucose pyrophosphorylase alone in COS cells had no effect on the glycogen level. However, coexpression of the hyperactive 2,3a glycogen synthase mutant with either glycogenin or UDP-glucose pyrophosphorylase led to higher glycogen accumulation than that obtained from the expression of glycogen synthase alone. Coexpression of glycogenin with the 2,3a mutant of glycogen synthase led to the appearance of glycogenin with a lower molecular weight suggestive of reduced glucosylation. Increased glycogen synthesis may lead to competition between glycogenin and glycogen synthase for their common substrate UDP-glucose. In summary, we conclude that (i) glycogen synthase is a primary rate-limiting enzyme of glycogen biosynthesis in COS cells, (ii) that phosphorylation of glycogen synthase is regulatory for glycogen accumulation, and (iii) once glycogen synthase is activated, the reaction mediated by UDP-glucose pyrophosphorylase can become rate-determining.
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PMID:Rate-determining steps in the biosynthesis of glycogen in COS cells. 864 5

The classic clinical presentation for type IV glycogen storage disease (branching enzyme deficiency, GSD IV) is hepatosplenomegaly with failure to thrive occurring in the first 18 months of life, followed by progressive liver failure and death by age 5 years. Although there have been two patients without apparent liver progression previously reported, no long-term follow-up clinical data have been available. We present here the clinical spectrum of the non-progressive liver form of GSD IV in four patients, and long-term follow-up of the oldest identified patients (ages 13 and 20 years). None has developed progressive liver cirrhosis, skeletal muscle, cardiac or neurological involvement, and none has been transplanted. Branching enzyme activity was also measured in cultured skin fibroblasts from patients with the classic liver progressive, the early neonatal fatal, and the non-progressive hepatic presentations of GSD IV. The residual branching enzyme activity in the patients without progression was not distinguishable from the other forms and could not be used to predict the clinical course. Our data indicate that GSD IV does not always necessitate hepatic transplantation and that caution should be used when counselling patients regarding the prognosis of GSD IV. Patients should be carefully monitored for evidence of progression before recommending liver transplantation.
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PMID:Clinical and laboratory findings in four patients with the non-progressive hepatic form of type IV glycogen storage disease. 883 Jan 77

Escherichia coli glycogen branching enzyme (GBE) and maize starch branching enzymes I (SBEI) and II (SBEII) were expressed in E. coli and purified. E. coli GBE branched amylose at a higher rate than did SBEII, but branched amylose at a lower rate than did SBEI. Similar to SBEI, GBE branched amylopectin at a lower rate than did SBEII. High-performance anion-exchange chromatography analysis of the branched products produced by BE revealed the minimum chain length (cl) required for branching. While GBE and SBEII showed the same minimum cl [degree of polymerization (dp) 12] required for branching, SBEI had a slightly higher minimum cl (dp 16) requirement for branching. The major differences between GBE and SBE are their specificities in terms of the size of chains transferred. In comparison with SBE, GBE had a much narrower size range of chains transferred and transferred mainly shorter chains. While SBEI and SBEII produced a large number of chains ranging from dp 6 to over dp 30, GBE predominantly transferred chains ranging from dp 5 to 16 and produced only a very small number of long chains with dp greater than 20. Although it has been reported that SBEI and SBEII preferentially transfer longer and shorter chains, respectively (1), this study further defines the differences between SBEI and SBEII in the size of chains transferred. SBEI predominantly transfers longer chains with dp greater than 10, while producing few shorter chains with dp 3 to 5. In contrast, SBEII preferentially transfers smaller chains with dp 3 to 9, with the most abundant chains being dp 6 and 7. The significance of minimum chain-length requirement by SBE is discussed in setting the invariant size of amylopectin cluster size (9 nm).
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PMID:Comparing the properties of Escherichia coli branching enzyme and maize branching enzyme. 918 17

The affinity of potato tuber starch-branching enzyme-I (PSBE-I) for various linear malto-oligosaccharides, cyclodextrins, (CDs) and macromolecular alpha-glucans was investigated by alpha-glucan induced fluorescence quenching of intrinsic PSBE-I tryptophan residues and by affinity electrophoresis. alpha-Glucan binding was characterised by distinct shifts towards shorter wavelengths of the PSBE-I fluorescence emission spectrum and by concomitant reductions in fluorescence intensity. The magnitudes of both the maximum shift in emission spectrum and reduction in fluorescence intensity were dependent on the alpha-glucan ligands used. Maximum Kd for a range of linear malto-oligosaccharides analysed was 0.13 mM as found at a degree of polymerisation (DP) of 13. Large differences in dissociation constants were measured for CDs with DP 6 (alpha-CD, 6.0 mM), DP 7 (beta-CD, 0.25 mM) and DP 8 (gamma-CD, 0.67 microM). The high-molecular-mass alpha-glucans amylose and amylopectin, both substrates for PSBE-I, showed apparent affinities of 0.018 and 0.066 mg/ml, respectively. Small linear and cyclic oligosaccharides competed with amylopectin in the affinity electrophoresis system and they were also competitive inhibitors for PSBE-I activity. The affinities for oligosaccharides as measured by competition were, however, about 10-fold lower than as measured by fluorescence quenching suggesting the existence of a separate oligosaccharide binding site on PSBE-I. Affinity electrophoresis revealed multiform heterogeneity in the enzyme preparation with respect to alpha-glucan interaction.
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PMID:Alpha-glucan binding of potato-tuber starch-branching enzyme I as determined by tryptophan fluorescence quenching, affinity electrophoresis and steady-state kinetics. 952 5

Glycogen storage disease type IV (GSD-IV) is a rare autosomal recessive disease caused by deficient glycogen branching enzyme (GBE). We report a 15-month-old female patient with GSD-IV who exhibited an abdominal distension and failure to thrive for 9 months. The patient showed hepatosplenomegaly with massive ascites. The laboratory findings showed abnormal liver functions including prolongation of prothrombin time and partial thromboplastin time. The light microscopic and electron microscopic findings of the liver biopsy specimen were consistent with GSD-IV. Measurement of glycogen quantity in the red blood cells showed increased storage of glycogen in the patient and interestingly, in her mother. The GBE activity of the patient's red blood cells was undetectable. The patient's ascites, general condition, and laboratory findings have been improved with supportive treatment with diuretics and a low dose of prednisolone.
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PMID:Glycogen storage disease type IV: a case report. 961 Jun 25

Rat brain glycogen branching enzyme was partially purified in order to elucidate its mechanism of action. The alpha1,4-alpha1,6-glucan polysaccharide was synthesized using rat brain branching enzyme under two different elongation conditions: Glc-1-P and phosphorylase or UDP-Glc and glycogen synthase. The products obtained demonstrated that the cpolysaccharides synthesized (pattern of the spectra obtained in the presence of Krisman's reagent, lambda max, parameter A and R, % beta-amylolysis and degree of branching) under different incubation times are nearly constant. These results imply that the degree of branching of a polysaccharide depends only on the enzyme specificity.
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PMID:Glycogen brain branching enzyme. 962 Apr 41

The branching enzyme belongs to the amylolytic family, a group of enzymes that cleave and/or transfer chains of glucan. The amylolytic enzymes are homologous and all contain four conserved regions, proposed to contain the active site. By primary structure analysis, a conserved position unique to branching enzymes has been identified. This residue, which is either Asp or Glu, depending on the species, is located immediately after the putative catalytic Glu-458 (Escherichia coli numbering). Branching enzymes differ from other amylolytic enzymes in having this acid pair, and we asked if this motif could be essential for branching enzyme action. We used site-directed mutagenesis of the Glu-459 residue in the E. coli branching enzyme in order to determine the significance of the conserved Asp/Glu in branching enzymes. A substitution of Glu-459 to Asp resulted in increased specific activity compared to wild-type, suggesting that the mutation had created a more efficient enzyme. Changing Glu-459 to Ala, Lys, or Gln lowered the specific activities and altered the preferred substrate from amylose to amylopectin.
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PMID:Glutamate-459 is important for Escherichia coli branching enzyme activity. 963 47


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