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Biomedical subjects

J Preiss

Publications and source records attributed to J Preiss.

At least 145 records · Page 8Linked to original sources
PubMed1986

Cloning and expression of the Escherichia coli glgC gene from a mutant containing an ADPglucose pyrophosphorylase with altered allosteric properties.

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.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1986

Physiological asymmetry of brain functions--its influence on the lateralization, symptomatology and course of the epileptic process.

Lateralization of the epileptic process in a group of 152 subjects and the relationship of epilepsy to the lateralization of brain functions was studied in smaller groups of 108 and 56 subjects. A unilateral epileptic process in the temporal limbic structures of the brain is localized in the left half of the brain twice (in 64.5%) to four times (in 80.8%) as often as in the right half. The greater the asymmetry of physiological brain functions--in particular motor and verbally symbolic functions--the more is this tendency pronounced. An epileptic process in temporal limbic structures of the left half of the brain is manifested more often in primarily generalized epileptic seizures with initial sudden and complete loss of consciousness. Episodic spike-and-wave activity, which is the typical electroencephalographic correlate of primarily generalized seizures, or of the thalamocortical aetiopathogenetic component of the epileptic process, is often asymmetrical in amplitude, which in 68.1% of these cases is twice as high over the left hemisphere. An epileptic process in subcortical structures of the right hemisphere impairs physiological asymmetry of emotive facial mimicry (with preponderance of mimic reactions on the left) and in 68.4% of the cases causes atypical preponderance of emotive mimicry in the right half of the face. A unilateral epileptic process in subcortical structures of the left half of the brain has a more favourable course and more hopeful prognosis in 70.4% of the cases, while the course of a right-sided process is worse in 67.6%.

Action Potentials↗
PubMed1985

Partial purification and characterization of granule-bound starch synthases from normal and waxy maize.

The granule-bound starch-synthases from normal and waxy maize kernels have been solubilized, partially purified, and characterized. Two broad categories of starch synthases were revealed with representatives in the soluble phase and also on granules from both normal and waxy maize though the activity associated with granules from waxy was small. Data for native molecular weights, kinetic parameters, and immunological relatedness are used to demonstrate that the granule-bound isozymes from normal maize are different from the soluble enzymes. These distinct granule-bound enzymes are missing in waxy maize granules and a further novel form of starch synthase is revealed. These findings are discussed in relation to the type of starch produced in tissue affected by the waxy mutation.

Journal Article↗
PubMed1985

Starch Branching Enzymes from Maize : Immunological Characterization using Polyclonal and Monoclonal Antibodies.

Spleen cells from mice immunized with starch branching enzymes were fused with cells from the mouse myeloma Sp2/0-AG14 cell line to form hybridomas. Those hybridomas producing antibodies against the branching enzyme were screened by the enzyme-linked immunosorbent assay using purified branching enzyme as the antigen. Three monoclonal cell lines (1A1D7, 1A1C3 and 4D2A9D8) were found to produce antibodies which showed positive enzyme-linked immunosorbent assay reactions with maize branching enzyme I in addition to branching enzymes IIa and IIb. Three other monoclonal cell lines (4D2D10, 4D2F9, and 2A6C12) were also selected which were found to produce antibodies showing positive enzyme-linked immunosorbent assay reactions with branching enzymes IIa and IIb only.Amino acid composition and peptide maps obtained after trypsin or chymotrypsin digestion show that there is no difference between branching enzyme IIa and IIb but they are significantly different from branching enzyme I which, along with immunological data, suggests that only two forms of starch branching enzyme may be present in maize kernels.Immunological cross-reaction was also found between the starch branching enzyme from maize kernels and the glycogen branching enzyme from Escherichia coli using polyclonal antibodies against starch branching enzyme I or IIa and IIb or E. coli glycogen branching enzyme, suggesting some immunological similarities between maize starch branching enzymes and E. coli glycogen branching enzyme.

Journal Article↗
PubMed1984

Biosynthesis of bacterial glycogen: characterization of adenosine diphosphate glucose synthetases from Enterobacter hafniae and Aeromonas hydrophila.

Enterobacter hafniae and Aeromonas hydrophila ADPglucose synthetases were purified approximately 39- and 61-fold, respectively, over the crude extract. Both enzymes were heat stable at 60 degrees C in the presence of inorganic phosphate. The molecular weights of both enzymes were approximately 200,000 which are similar to other enteric ADPglucose synthetases studied. Based on kinetic results obtained from the partially purified enzymes, the E. hafniae enzyme is activated twofold by phospho-enolpyruvate while the A. hydrophila enzyme is activated twofold by fructose 6-P and 1.5-fold by fructose 1,6 bis-phosphate. The E. hafniae enzyme activity is strongly inhibited by AMP and ADP and the inhibition can be partially reversed by P-enolpyruvate. ADP is the most effective inhibitor of the A. hydrophila enzyme and its inhibition can be partially overcome by the presence of the activators fructose 6-P and fructose 1,6-P2. These kinetic results show that the allosteric properties of the E. hafniae enzyme are distinctly different from the ADPglucose synthetases of those previously studied from bacteria of the genus Enterobacter. Although the A. hydrophila enzyme is activated by fructose 1,6-P2, its allosteric properties are quite different than those observed for ADPglucose synthetase of the Enterobacteriaceae.

Adenosine Diphosphate↗
PubMed1984

ADPglucose Pyrophosphorylase from the CAM Plants Hoya carnosa and Xerosicyos danguyi.

ADPglucose pyrophosphorylase from the Crassulacean acid metabolism plants Hoya carnosa and Xerosicyos danguyi were partially purified to study their regulatory and kinetic properties. The molecular weight of the native enzymes from both plants was determined to be about 209,000. The enzyme from both plants was found to be activated by glycerate 3-phosphate and inhibited by inorganic phosphate. The kinetic constants for the substrates and Mg(2+) are reported. The significance of the activation by glycerate 3-phosphate and inhibition by inorganic phosphate of ADPglucose synthesis catalyzed by the H. carnosa and X, danguyi enzymes is discussed. ADPglucose synthesized by the above enzymes was found to be the most effective donor of the glucosyl portion to alpha-glucan primer in the starch synthase reaction observed in CAM plants.

Journal Article↗
PubMed1983

Pyrophosphate may be involved in regulation of bacterial glycogen synthesis.

Inorganic pyrophosphate is a potent inhibitor of the enzyme that catalyzes synthesis of the glucosyl donor for Escherichia coli glycogen synthesis, ADP-glucose pyrophosphorylase. The Ki is determined to be 40 microM and the substrate ATP, the activator, fructose 1,6-P2 or the allosteric inhibitor, AMP do not greatly affect the inhibition. PPi exhibits mixed type inhibition with the other substrate, glucose 1-P. The potential regulation of glycogen synthesis by PPi is discussed.

Adenosine Diphosphate Glucose↗
PubMed1983

Biosynthesis of bacterial glycogen. Primary structure of Escherichia coli ADP-glucose synthetase as deduced from the nucleotide sequence of the glg C gene.

The nucleotide sequence of the glg C gene of Escherichia coli K12, coding for ADP-glucose synthetase, has been determined. The structural gene consists of 1293 base pairs, which specify a protein of 431 amino acids. The amino acid sequence deduced from the DNA sequence is consistent with the known NH2-terminal amino acid sequence and the amino acid composition of ADP-glucose synthetase. The translation start of the structural gene of glycogen synthase, glg A, starts immediately after termination of the glg C gene.

Amino Acid Sequence↗
PubMed1983

Biosynthesis of bacterial glycogen: activator specificity of the ADPglucose pyrophosphorylase of Rhodopseudomonads.

The adenosine diphosphate glucose pyrophosphorylases from Rhodopseudomonas acidophila, Rhodopseudomonas blastica, Rhodopseudomonas globiformis, and Rhodopseudomonas viridis were purified to the extent that their regulatory properties could be studied. With the exception of the R. viridis enzyme, all the enzymes could be activated by pyruvate or its analog, oxamate. The most effective activator for all the enzymes was fructose 6-P. However, the R. globiformis and R. viridis ADP glucose pyrophosphorylases can also be activated by fructose 1,6-P2. Thus a new activator specificity class was observed for the R. viridis enzyme while the R. acidophila and R. blastica enzymes exhibited the same activator specificity previously observed for Rhodopseudomonas capsulata ADPglucose pyrophosphorylase. The R. globiformis enzyme, activated by fructose 6-P, fructose 1,6-P2, and by pyruvate had a similar activator specificity previously seen for the Rhodopseudomonas sphaeroides and Rhodopseudomonas gelatinosa enzymes. For some enzymes, the presence of activator increased the apparent affinity for the substrates and MgCl2. The activator also modulated the sensitivity of the R. viridis and R. acidophila enzymes to Pi inhibition and the R. blastica enzyme to AMP inhibition. ADPglucose is the glucosyl donor for glycogen synthesis in these bacteria. Thus, regulation of glycogen synthesis in these microorganisms is probably regulated by the ratio of the activator concentration to inhibitor concentration.

Bacterial Proteins↗
PubMed1983

Regulation of bacterial glycogen synthesis.

The formation of the alpha 1,4 glucosidic linkages of bacterial glycogen occurs first by synthesis of ADPglucose from ATP and alpha glucose 1-P and then transfer of the glucose moiety from the formed sugar nucleotide to a pre-existing glucan primer. Unlike mammalian glycogen synthesis, regulation occurs at the synthesis of the sugar nucleotide. Generally glycolytic intermediates activate ADPglucose synthesis while AMP, ADP and/or Pi inhibit ADPglucose synthesis. A variation of activator specificity is is seen when the enzyme is isolated from different bacteria and is thought to be related to the predominant type of carbon assimilation or dissimilation pathways present in the particular organism. Evidence indicating that the allosteric activation effects observed in vitro are physiologically pertinent for the regulation of glycogen synthesis is reviewed. The recent experiments in identifying the allosteric activator site of the Escherichia coli ADPglucose pyrophosphorylase as well as other chemical modification studies identifying amino acid residues essential for allosteric activation and for catalytic activity are discussed. Evidence is also presented for the covalent modification of the Rhodopseudomonas sphaeroides ADPglucose pyrophosphorylase by bromopyruvate at its allosteric activator site. Regulation of the biosynthesis of glycogen also occurs at the genetic level and the current evidence for the existence of a glycogen operon is presented. In addition the current studies concerning the cloning of the DNA region containing the Escherichia coli structural genes coding for the glycogen biosynthetic enzymes as well as the nucleotide sequence of the E. coli ADPglucose pyrophosphorylase are presented.

Adenosine Diphosphate Glucose↗
PubMed1983

Solubilization of the starch-granule-bound starch synthase of normal maize kernels.

The starch-granule-bound starch synthase from Zea mays has been solubilized with a recovery of between 50 and 84%. Chromatography of the solubilized enzyme on DEAE-Sepharose resolves two fractions of activity which may be distinguished by their response to citrate. Neither solubilized isoenzyme displays any significant activity with UDPglucose.

Journal Article↗
PubMed1983

Spinach Leaf Intra and Extra Chloroplast Phosphorylase Activities during Growth.

The amino terminal sequence of the spinach (Spinacia oleracea L. cv Bloomsdale Long Standing) leaf cytoplasmic phosphorylase was determined and shown to have little similarity to the known sequence of the potato tuber phosphorylase. The antigenic reaction of spinach chloroplast phosphorylase and rabbit muscle phosphorylase a to antiserum prepared against spinach leaf cytoplasmic phosphorylase was tested. Neither phosphorylase gave a positive reaction when tested by immunodiffusion or neutralization of enzyme activity. The two spinach phosphorylases were assayed throughout the growth of the plant. Activity of cytoplasmic phosphorylase increased 4- to 8-fold at 30 to 35 days from sowing. Enzyme protein levels, as measured by antibody neutralization, increased by a similar amount. There was no corresponding increase in chloroplast phosphorylase activity. The chloroplast phosphorylase varied in parallel with the chloroplast enzyme ADPglucose pyrophosphorylase. Starch levels were high during the earlier stages of growth and then fell to a constant low level just before the increase in cytoplasmic phosphorylase. The results are discussed with respect to the relationship and functions of the two phosphorylases.

Journal Article↗
PubMed1983

Regulation of ADPGlucose Synthesis in Guard Cells of Commelina communis.

The activator specificity of the ADPglucose pyrophosphorylase from Commelina communis guard cells is the same as observed for the mesophyll cell enzyme. 3-Phosphoglycerate was found to be the most effective activator. Fifty per cent of maximal stimulation was observed at about 100 micromolar. Inorganic phosphate was found to be a potent inhibitor giving 50% inhibition at 0.3 millimolar. These results are discussed with respect to regulation of starch synthesis in guard cells.

Journal Article↗
PubMed1983

ATP-Dependent Proteolytic Activity from Spinach Leaves.

Spinach (Spinacia oleracea CV Bloomsdale Long Standing) leaf cytoplasmic starch phosphorylase and rabbit muscle phosphorylase a were inactivated by incubation with partially purified leaf extract in the presence of ATP and Mg(2+). The inactivating factor(s) were heat stable and susceptible to protease attack. Phosphorylase inactivation was prevented by incubation in the presence of p-aminobenzamidine and phenylboronic acid, or prolonged treatment with phenylmethylsulfonyl fluoride or leupeptin for the ATP-stimulated inhibitory activity. Mg(2+) -dependent inactivation was prevented by incubation with leupeptin, phenylmethylsulfonyl fluoride, p-aminobenzamidine, or 5'-adenylate. ATP-mediated inactivation of phosphorylase was stimulated by Mg(2+) with a reduction in the apparent K(m) for ATP. Casein-degrading activities with the same properties of ATP and/or Mg(2+) stimulation, heat stability, and susceptibility to proteinase inhibitors were detected suggesting that phorphorylase inactivation was due to proteolysis. The activity was greatest at about the time of flowering and also appeared to depend on the light regime.

Journal Article↗