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)

An Escherichia coli B mutant, SG14, accumulates glycogen at 28% the rate observed for the parent E. coli B strain. The glycogen accumulated in the mutant is similar to the glycogen isolated from the parent strain with respect to alpha- and beta-amylosis, chain length determination, and I2-complex absorption spectra. The SG14 mutant contains normal glycogen synthase and branching enzyme activity but has an ADP-glucose pyrophosphorylase with altered kinetic and allosteric properties. The mutant enzyme has been partially purified and requires a 12-fold higher concentration of fructose-P2 or a 26 fold higher concentration of pyridoxal-P than the parent type enzyme for 50% of maximal allosteric activation. TPNH, an effective activator of the E. coli B enzyme, does not activate the SG14 ADP-glucose pyrophosphorylase. Other studies show that for the SG14 enzyme the concentrations of ATP and Mg2+ in the synthesis direction and the concentrations of ADP-glucose and PPi in the pyrophosphorolysis direction required to give 50% of maximal activity are 3- to 6-fold higher than those observed for the parent E. coli B ADP-glucose pyrophosphorylase. The Km for alpha-glucose-1-P at saturating to half-saturating concentrations of the activator, fructose-P2, are about the same for both enzymes. However, in the presence of no activator, the concentration of glucose-1-P required for half-maximal activity is about 1.8-fold higher for the SG14 enzyme. Thus SG14 ADP-glucose pyrophosphorylase has lower affinity for its substrates than does the parent enzyme. Previously the SG14 enzyme had been shown to be less sensitive to inhibition by 5'-AMP than the E. coli B enzyme. This ensensitivity to inhibition renders the SG14 enzyme less responsive to energy charge than the E. coli B ADP-glucose pyrophosphorylase. On the basis of the above results and taking into account the reported concentrations of fructose-P2, of pyridoxal-P, and of the adenine nucleotide pool and its energy charge in E. coli strains, it is concluded that furctose-P2 is the important physiological allosteric activator of E. coli ADP-glucose pyrophosphorylase. Furthermore, the 1.7-fold increased rate of accumulation of glycogen observed when E. coli B or SG14 shifts from exponential phase to stationary phase of growth in nitrogen-limiting media can be accounted for by the 2.4-fold increase of the levels of the glycogen biosynthetic enzymes, glycogen synthase, and ADP-glucose pyrophosphorylase. Thus both allosteric regulation of the ADP-glucose pyrophosphorylase as well as the genetic regulation of the biosynthesis of the glycogen biosynthetic enzymes are involved in the regulation of glycogen accumulation in E. coli B.
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PMID:Biosynthesis of bacterial glycogen. Kinetic studies of a glucose-1-phosphate adenylyltransferase (EC 2.7.7.27) from a glycogen-deficient mutant of Escherichia coli B. 24 Aug 34

Structural gene mutants of the glycogen biosynthetic enzymes adenosine diphosphate glucose pyrophosphorylase (glgC) and glycogen synthase (glgA) were isolated and partially characterized. The cotransduction frequencies of these genes with the aspartic semialdehyde dehydrogenase (asd) and glycerol-3-phosphate dehydrogenase (glpD) genes suggested the unambiguous gene order of glpD glgA glgC asd. The results of the three-factor cross glpD- glgA- glgC+ X glpD+ glgA+ glgC- were consistent with the proposed order. A simultaneous and approximately equivalent derepression of the glgC, glgA, and glgB (branching enzyme) gene products was observed in the late logarithmic-early stationary phase of growth on enriched media. These results are consistent with the coordinately regulated synthesis of the three glycogen biosynthetic enzymes in Salmonella typhimurium.
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PMID:Biosynthesis of bacterial glycogen: genetic and allosteric regulation of glycogen biosynthesis in Salmonella typhimurium LT-2. 40 93

We have cloned the structural gene for the Bacillus caldolyticus glycogen branching enzyme (glgB) in Escherichia coli. The glgB gene consisted of a 1998 bp open reading frame (ORF) encoding a 78,087 Da protein, which was highly similar to the Bacillus stearothermophilus branching enzyme. The 5' end of a second gene that encoded a protein with extensive similarity to E. coli ADP-glucose pyrophosphorylase (ADPGP) partly overlapped the 3' end of the glgB gene. A putative promoter recognized by Bacillus subtilis RNA polymerase containing the sigma factor H (E-sigma H) preceded the genes. These data suggest that in contrast to the situation observed in B. stearothermophilus, the genes involved in glycogen synthesis in B. caldolyticus are clustered on the chromosome, and are presumably coordinately expressed during the early stages of sporulation. An incomplete third gene started upstream of B. caldolyticus glgB. This gene was highly similar to a gene found directly upstream of B. stearothermophilus glgB, which encodes a putative membrane protein with unknown function. The B. caldolyticus glgB gene was expressed in E. coli and B. subtilis. Surprisingly, the branching enzyme appeared to be thermolabile, the temperature of optimal activity being only 39 degrees C.
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PMID:The glgB gene from the thermophile Bacillus caldolyticus encodes a thermolabile branching enzyme. 129 17

One of the key enzymes involved in the formation of amylopectin, which is the major component of starch, is branching enzyme. A cDNA for potato branching enzyme was cloned by screening a tuber-specific cDNA expression library using an antiserum directed against a denatured preparation of the protein. Complementation of an Escherichia coli strain deficient in branching enzyme was achieved using a construct derived from this clone. Analysis of the expression of the gene in potato revealed a close association with conditions favouring starch biosynthesis. The expression pattern of the gene coding for potato branching enzyme, as analyzed at the mRNA level, closely resembles that of AGPase S, a gene coding for one of the subunits of ADP-glucose pyrophosphorylase, which is the key regulatory enzyme in the starch biosynthetic pathway. This raises the possibility that enzymes involved in the pathway are coordinately regulated at the transcriptional level.
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PMID:Cloning and expression analysis of a potato cDNA that encodes branching enzyme: evidence for co-expression of starch biosynthetic genes. 174 41

Potato tubers are modified stems that have differentiated into storage organs. Factors such as day-length, nitrogen supply, and levels of the phytohormones cytokinin and gibberellic acid, are known to control tuberization. Morphological changes during tuber initiation are accompanied by the accumulation of a characteristic set of proteins, thought to be involved in N-storage (i.e. patatin) or defense against microbial or insect attack (i.e. proteinase inhibitor II). Additionally, deposition of large amounts of starch occurs during tuber formation, which is paralleled by an increase in sucrose synthase and other enzymes involved in starch biosynthesis (i.e. ADP-glucose pyrophosphorylase, starch synthases, and branching enzyme). Potential controlling mechanisms for genes expressed during tuberization are discussed.
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PMID:Gene expression during tuber development in potato plants. 220 Jul 13

We have isolated a region from the Bacillus stearothermophilus CU21 chromosome hybridizing strongly to a fragment of the B. caldolyticus glycogen operon. Sequence analysis of this region revealed the presence of a truncated glgB gene encoding the N-terminus of branching enzyme. A region highly similar to an internal fragment of B. caldolyticus glgC encoding ADP-glucose pyrophosphorylase was located approximately 1kb downstream from the incomplete glgB gene. The two truncated genes appeared to flank a sequence with characteristics of bacterial Insertion Sequences, which was designated RSBst-alpha. The presence of RSBst-alpha at this position indicates that integration of (an) IS-like element(s) may have been involved in deletion formation in the putative glycogen operon. Upstream of glgB an additional incomplete ORF was found with significant similarity to putative transposases from bacterial Insertion Sequences. This region was designated RSBst-beta. Both RSBst-alpha and RSBst-beta appeared to be present in multiple copies in the B. stearothermophilus CU21 chromosome.
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PMID:Two putative insertion sequences flank a truncated glycogen branching enzyme gene in the thermophile Bacillus stearothermophilus CU21. 831

Antibodies were used to probe the degree of association of starch biosynthetic enzymes with starch granules isolated from maize (Zea mays) endosperm. Graded washings of the starch granule, followed by release of polypeptides by gelatinization in 2% sodium dodecyl sulfate, enables distinction between strongly and loosely adherent proteins. Mild aqueous washing of granules resulted in near-complete solubilization of ADP-glucose pyrophosphorylase, indicating that little, if any, ADP-glucose pyrophosphorylase is granule associated. In contrast, all of the waxy protein plus significant levels of starch synthase I and starch branching enzyme II (BEII) remained granule associated. Stringent washings using protease and detergent demonstrated that the waxy protein, more than 85% total endosperm starch synthase I protein, and more than 45% of BEII protein were strongly associated with starch granules. Rates of polypeptide accumulation within starch granules remained constant during endosperm development. Soluble and granule-derived forms of BEII yielded identical peptide maps and overlapping tryptic fragments closely aligned with deduced amino acid sequences from BEII cDNA clones. These observations provide direct evidence that BEII exits as both soluble and granule-associated entities. We conclude that each of the known starch biosynthetic enzymes in maize endosperm exhibits a differential propensity to associate with, or to become irreversibly entrapped within, the starch granule.
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PMID:Physical association of starch biosynthetic enzymes with starch granules of maize endosperm. Granule-associated forms of starch synthase I and starch branching enzyme II. 875 83

The aim of the work described in this paper was to characterize the tubers of potato (Solanum tuberosum var. Prairie) plants that had been transformed with the Escherichia coli ADPglucose pyrophosphorylase (EC 2.7.7.27) gene, glgC-16, under the control of a patatin promoter. Over 30 lines of transformed plants with increased ADPglucose pyrophosphorylase activity were obtained. The tubers of six of these lines were compared with those of control plants expressing the gene for beta-glucuronidase. The average increase in pyrophosphorylase activity was 200%, and the highest was 400%. Western immunoblotting of tuber extracts showed that the amounts of glgC-16 protein were linearly related to the extractable activity of the ADPglucose pyrophosphorylase. Cell fractionation studies showed that the increased activity of the pyrophosphorylase in the glgC-16 tubers had a similar intracellular location, the amyloplast fraction, to that found in the control tubers. No pleiotropic changes in the maximum catalytic activities of the following enzymes could be detected in the glgC-16 tubers: sucrose synthase, fructokinase, UDPglucose pyrophosphorylase, phosphofructokinase, soluble starch synthase, starch branching enzyme, phosphoglucomutase and alkaline inorganic pyrophosphatase. The glgC-16 tubers are held to be suitable for the study of the role of ADPglucose pyrophosphorylase in the control of starch synthesis.
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PMID:Characterization of transgenic potato (Solanum tuberosum) tubers with increased ADPglucose pyrophosphorylase. 897 57

A chromosomal region of Bacillus stearothermophilus TRBE14 which contains genes for glycogen synthesis was cloned and sequenced. This region includes five open reading frames (glgBCDAP). It has already been demonstrated that glgB encodes branching enzyme (EC 2.4.1.18 [H. Takata et al., Appl. Environ. Microbiol. 60:3096-3104, 1994]). The putative GlgC (387 amino acids [aa]) and GlgD (343 aa) proteins are homologous to bacterial ADP-glucose pyrophosphorylase (AGP [EC 2.7.7.27]): the sequences share 42 to 70% and 20 to 30% identities with AGP, respectively. Purification of GlgC and GlgD indicated that AGP is an alpha2beta2-type heterotetrameric enzyme consisting of these two proteins. AGP did not seem to be an allosteric enzyme, although the activities of most bacterial AGPs are known to be allosterically controlled. GlgC protein had AGP activity without GlgD protein, but its activity was lower than that of the heterotetrameric enzyme. The GlgA (485 aa) and GlgP (798 aa) proteins were shown to be glycogen synthase (EC 2.4.1.21) and glycogen phosphorylase (EC 2.4.1.1), respectively. We constructed plasmids harboring these five genes (glgBCDAP) and assayed glycogen production by a strain carrying each of the derivative plasmids on which the genes were mutated one by one. Glycogen metabolism in B. stearothermophilus is discussed on the basis of these results.
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PMID:Characterization of a gene cluster for glycogen biosynthesis and a heterotetrameric ADP-glucose pyrophosphorylase from Bacillus stearothermophilus. 924 54

The gene organization and transcription of the Agrobacterium glg operon differ from those in other bacteria. Agrobacterium tumefaciens A348 contains a 9.1-kb gene cluster harboring genes for glycogen metabolism. The nucleotide sequence and gene organization of a region containing ADP-glucose pyrophosphorylase (glgC), glycogen synthetase (glgA), and phosphoglucomutase (pgm) genes have been previously described (A. Uttaro and R. A. Ugalde, Gene 150:117-122, 1994). In this work we report that the glycogen phosphorylase (glgP) and branching enzyme (glgB) genes are located immediately upstream of this region. The complete nucleotide sequences of the glgP and glgB genes were obtained, and mutants were constructed by targeted insertional mutagenesis with a kanamycin cassette. Enzymatic assays and reverse transcription PCR carried out with the wild type and with glgP and glgB mutants, as well as primer extension experiments and beta-galactosidase fusions, revealed that this region containing five open reading frames (glgPBCA and pgm) is transcribed unidirectionally as a single operon under the control of a promoter located upstream of the glycogen phosphorylase gene (glgP). An alternative transcript was identified starting 168 bp upstream of an internal ATG start codon of the pgm gene, which is translated as a 71-amino-acid-shorter Pgm protein which complements in vivo a pgm mutant. This alternative transcript has a promoter with the motif TATCAAN5G, identified in octopine Ti plasmid as an autoinducible TraR promoter. This promoter is >200 times more efficient in A. tumefaciens than in Escherichia coli, as judged by the level of enzymatic activity of a lacZ-pgm fusion.
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PMID:Gene organization and transcription analysis of the Agrobacterium tumefaciens glycogen (glg) operon: two transcripts for the single phosphoglucomutase gene. 985 99


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