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J Preiss

Publications and source records attributed to J Preiss.

At least 55 records · Page 3Linked to original sources
PubMed1997

Analysis of data about epileptic patients using the GUHA method.

In this paper we search for hypotheses on association between the memory quotient and 13 clinical variables examined in a sample of 214 epilepsy patients. We introduce the General Unary Hypotheses Automaton (GUHA) method that automatically generates hypotheses from empirical data by means of computer procedures. Procedure ASSOC of the program GUHA generates and evaluates the hypotheses on symmetrical association or asymmetrical association using quantifiers. The most used symmetrical and asymmetrical quantifiers of the ASSOC procedure are introduced. Data analysis on epileptic patients using the GUHA method is done and the results are presented. We propose a new interpretation of the results including a graphical presentation.

Age of Onset↗
PubMed1996

Control of starch composition and structure through substrate supply in the monocellular alga Chlamydomonas reinhardtii.

In Chlamydomonas, as in higher plants, synthesis of ADP glucose catalyzed by ADP-glucose pyrophosphorylase is rate-limiting for the building of starch in the chloroplast. We have isolated disruptions of the STA1 ADP-glucose pyrophosphorylase structural gene that rendered the enzyme less responsive to the allosteric activator 3-phosphoglycerate. The structure and composition of the residual starch synthesized by all mutants of the STA1 locus is dramatically altered. The residual polysaccharide is shown to be devoid of amylose despite the presence of granule-bound starch synthase, the amylose biosynthetic enzyme. In addition, the fine structure of the mutant amylopectin revealed the presence of an altered chain-length distribution. This distribution mimicks that which is observed during growth and photosynthesis and differs markedly from that observed during storage. We therefore propose that low nucleotide sugar concentrations are either directly or indirectly responsible for the major differences observed in the composition or structure of starch during storage and photosynthesis.

Amylopectin↗
PubMed1996

Site-directed mutagenesis of lysine382, the activator-binding site, of ADP-glucose pyrophosphorylase from Anabaena PCC 7120.

Previous studies have shown that a highly conserved lysyl residue (Lys 419) near the C-terminus of Anabaena ADP-glucose pyrophosphorylase is involved in the binding of 3-P-glycerate, the allosteric activator [Charng, Y., Iglesias, A. A., & Preiss, J. (1994) J. Biol. Chem. 269, 24107-24113]. Phosphopyridoxylation of the K419R mutant enzyme modified another conserved lysyl residue (Lys382), suggesting that this residue might be also located within the activator-binding site [Charng, Y., Iglesias, AA., & Preiss, J. (1994) J. Biol. Chem. 269, 24107-24113]. Site-directed mutagenesis of Lys382 of the Anabaena enzyme was performed to determine the role of this residue. Replacing Lys382 with either arginine, alanine, or glutamine produced mutant enzymes with apparent affinities for 3-P-glycerate 10-160-fold lower than that of the wild-type enzyme. The glutamic acid mutant enzyme was inhibited by 3-P-glycerate. These mutations had lesser impact on the kinetic constants for the substrates and inhibitor, P(i), and on the thermal stability. These results indicate that both the charge and size of the residue at position 382 influence the binding of 3-P-glycerate. Site-directed mutagenesis was also performed to obtain a K382R-K419R double mutant. The apparent affinity for 3-P-glycerate of this double-mutant enzyme was 104-fold lower than that of the wild-type enzyme, and the specificity for activator of this mutant enzyme was altered. The K382R-K419R enzyme could not be phosphopyridoxylated, suggesting that other lysine residues are not involved in the binding of 3-P-glycerate.

Allosteric Regulation↗
PubMed1996

Mutagenesis of the potato ADPglucose pyrophosphorylase and characterization of an allosteric mutant defective in 3-phosphoglycerate activation.

ADPglucose pyrophosphorylase (glucose-1-phosphate adenylyltransferase; ADP:alpha-D-glucose-1-phosphate adenylyltransferase, EC 2.7.7.27) catalyzes a key regulatory step in alpha-glucan synthesis in bacteria and higher plants. We have previously shown that the expression of the cDNA sequences of the potato tuber large (LS) and small (SS) subunits yielded a functional heterotetrameric enzyme capable of complementing a mutation in the single AGP (glgC) structural gene of Escherichia coli. This heterologous complementation provides a powerful genetic approach to obtain biochemical information on the specific roles of LS and SS in enzyme function. By mutagenizing the LS cDNA with hydroxylamine and then coexpressing with wild-type SS in an E. coli glgC- strain, >350 mutant colonies were identified that were impaired in glycogen production. One mutant exhibited enzymatic and antigen levels comparable to the wild-type recombinant enzyme but required 45-fold greater levels of the activator 3-phosphoglycerate for maximum activity. Sequence analysis identified a single nucleotide change that resulted in the change of Pro-52 to Leu. This heterologous genetic system provides an efficient means to identify residues important for catalysis and allosteric functioning and should lead to novel approaches to increase plant productivity.

Allosteric Regulation↗
PubMed1996

Evidence for essential arginine residues at the active sites of maize branching enzymes.

Alignment of 23 branching enzyme (BE) amino acid sequences from various species showed conservation of two arginine residues. Phenylglyoxal (PGO) was used to investigate the involvement of arginine residues of maize BEI and BEII in catalysis. BE was significantly inactivated by PGO in triethanolamine buffer at pH 8.5. The inactivation followed a time- and concentration-dependent manner and showed pseudo first-order kinetics. Slopes of 0.73 (BEI) and 1.05 (BEII) were obtained from double log plots of the observed rates of inactivation against the concentrations of PGO, suggesting that loss of BE activity results from as few as one arginine residue modified by PGO. BE inactivation was positively correlated with [14C]PGO incorporation into BE protein and was considerably protected by amylose and/or amylopectin, suggesting that the modified arginine residue may be involved in substrate binding or located near the substrate-binding sites of maize branching enzymes I and II.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1996

Analysis of the active center of branching enzyme II from maize endosperm.

Analysis of the primary structure of mBEII, with those of other branching and amylolytic enzymes as reference, identifies four highly conserved regions which may be involved in substrate binding and in catalysis. When one of the amino acid residues corresponding to the putative catalytic sites of mBEII, i.e., Asp-386, Glu-441, and Asp-509, was replaced, activity disappeared. These putative catalytic residues are located in three different regions (regions 2-4) of the four highly conserved regions (regions 1-4) which exist in the primary structure of most starch hydrolases and related enzymes, including branching enzymes. Region 3, which contains Glu-441 as one of the putative catalytic residues, was located downstream of the carboxyl-terminal position previously reported. The importance of the carboxyl amino acid residues was also demonstrated by chemical modification of the branching enzyme protein using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1996

ADPglucose pyrophosphorylase: basic science and applications in biotechnology.

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.

Amino Acid Sequence↗
PubMed1996

[Correlation of neuropsychological tests and density of brain white matter in schizophrenia].

In a group of 10 subjects, nine schizophrenic patients and one healthy twin (seven men and three women, i.e. two monozygotic twin pairs: two patients and a healthy man and his sick twin brother, one dizygotic pair of two female patients, three male patients and one female patient without their appropriate twin siblings) Halstead-Reitan Neuropsychological Battery (HRNB) was used and partial neuropsychological tests (Wechsler Memory Scale, the Stroop Color-Word Test, Tonal Memory). The parameters of white matter density were evaluated by computed tomography. The fundamental findings include: In our small group numerous statistically significant correlations were found between neuropsychological tests and white matter density. 2. Higher density is associated with poorer neuropsychological efficiency. There are very similar correlations between neuropsychological variables and density parameters in different areas of the brain. 4. The majority of correlations of neuropsychological parameters is from the area of tactile and motor functions. 5. It is striking that there are statistically significant correlations of density with the simultaneous performance of both hands and the performance of the non-dominant hand but not with the performance of the dominant hand alone. 6. Some correlations pertain in addition to density also to the very controversial problem of the brain size of schizophrenic patients. In the investigated group an association between better neuropsychological performance and larger size of the brain was found. All findings will have to be tested in larger groups of patients and healthy subjects.

Adult↗
PubMed1995

Mutagenesis of an amino acid residue in the activator-binding site of cyanobacterial ADP-glucose pyrophosphorylase causes alteration in activator specificity.

The specificity for activator of ADP-glucose pyrophosphorylase is closely related to the corresponding major carbon-assimilation pathway. The enzyme from Escherichia coli is mainly activated by fructose-1,6-P2, while the cyanobacterial, algal, and higher-plant enzymes are activated by 3-P-glycerate. Previous results have shown that Lys39 of the E. coli enzyme is involved in the binding of fructose-1,6-P2 while for the Anabaena enzyme, lysine residues 382 and 419 have been shown to be involved in the binding of 3-phosphoglycerate. This report shows that if Lys419 of the Anabaena enzyme is changed to glutamine, activation of the cyanobacterial enzyme by fructose-1,6-P2 becomes more effective than that of 3-P-glycerate at lower concentrations. Kinetic studies show that fructose-1,6-P2 competitively inhibits 3-P-glycerate activation of the Anabaena wild-type enzyme, suggesting that these two compounds bind to the same site. Thus a change of one amino acid at the activator binding domain can affect the specificity of activation of the Anabaena ADP-glucose pyrophosphorylase.

Allosteric Regulation↗
PubMed1995

Maize branching enzyme catalyzes synthesis of glycogen-like polysaccharide in glgB-deficient Escherichia coli.

The structure of alpha-glucan, isolated from wild-type Escherichia coli B, a glycogen branching enzyme (BE)-deficient E. coli AC71 (glgB-), or from AC71 transformed with genes coding for maize BEI and BEII individually as well as with both genes, was analyzed by high-performance anion-exchange chromatography (HPAEC) with pulsed amperometric detection. Transformation of the maize BE gene(s) in AC71 (glgB-) showed complementation in branching activity. Analysis by HPAEC revealed different structures between glycogen of E. coli B and alpha-glucan of AC71 transformed with a different maize BE gene(s). The individual chains of the alpha-glucan debranched with isoamylase were distributed between chain length (CL) 3 and > 30 and the chain with CL 6 was the most abundant. In comparison with the glycogen of E. coli B, the alpha-glucan of AC71 transformed with the maize BE gene(s) consisted of a lesser amount of chains with CL 7-9 and a larger amount of chains with CL > 14. It also showed a broad peak with chains of CL 9-12 as in maize amylopectin. This study provides in vivo evidence that glycogen BE and maize BE isozymes may have different specificities in the length of chain transferred. Furthermore, this study suggests that the specificity of glycogen synthase and starch synthase and their concerted action with BE play an important role in determining the structure of the polysaccharide synthesized.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1995

A capillary zone electrophoresis assay for the nucleoside transfer enzyme adenosine diphosphate-glucose pyrophosphorylase.

Conditions are described for a capillary zone electrophoresis-based assay of ADP-glucose pyrophosphorylase, the first enzyme in the de novo synthesis for alpha-glucan synthesis in plants and bacteria. ATP, ADP-glucose, and other adenine derivatives are effectively resolved and quantified in 12 min of electrophoresis. The method requires minimal sample manipulations and no postincubation hydrolyses, is effective over a wide range of enzyme and substrate concentrations, has a sensitivity comparable to radioisotope assays, and yields reproducible results in either the forward and reverse directions. Moreover, the assay is applicable to other enzymes that utilize nucleosides or their bases as substrates or products.

Adenine Nucleotides↗
PubMed1995

Adenosine 5'-diphosphate-glucose pyrophosphorylase from potato tuber. Significance of the N terminus of the small subunit for catalytic properties and heat stability.

cDNAs encoding the large subunit and a possibly truncated small subunit of the potato tuber (Solanum tuberosum L.) adenosine 5'-diphosphate-glucose pyrophosphorylase have been expressed in Escherichia coli (A.A. Iglesias, G.F. Barry, C. Meyer, L. Bloksberg, P.A. Nakata, T. Greene, M.J. Laughlin, T.W. Okita, G.M. Kishore, J. Preiss, J Biol Chem [1993] 268: 1081-1086). However, some properties of the transgenic enzyme were different from those reported for the enzyme from potato tuber. In this work, extension of the cDNA was performed to elongate the N terminus of the truncated small subunit by 10 amino acids. This extension is based on the almost complete conservation seen at the N-terminal sequence for the potato tuber and the spinach leaf small subunits. Expressing the extended cDNA in E. coli along with the large subunit cDNA yielded a transgenic heterotetrameric enzyme with similar properties to the purified potato tuber enzyme. It was also found that the extended small subunit expressed by itself exhibited high enzyme activity, with lower affinity for activator 3-phosphoglycerate and higher sensitivity toward inorganic phosphate inhibition. It is proposed that a major function of the large subunit of adenosine 5'-diphosphate-glucose pyrophosphorylases from higher plants is to modulate the regulatory properties of the native heterotetrameric enzyme, and the small subunit's major function is catalysis.

Amino Acid Sequence↗
PubMed1994

Allosteric sites of the large subunit of the spinach leaf ADPglucose pyrophosphorylase.

Pyridoxal-P, an analog of 3-phosphoglycerate, activates spinach leaf ADPglucose pyrophosphorylase. Reductive phosphopyridoxylation of the enzyme yields enzyme less dependent on the presence of activator for activity. Labeled pyridoxal-P is incorporated into both the 51- and 54-kDa subunits of the enzyme. The sequence of the single tryptic labeled peptide of the small subunit has been reported (Morell, M., Bloom, M., and Preiss, J. (1988) J. Biol. Chem. 263, 633-637). Three distinct labeled peptides are isolated from the tryptic digest of the large subunit. 3-Phosphoglycerate inhibits incorporation of pyridoxal-P by 80% into all three large subunit tryptic peptides, whereas inorganic phosphate, the allosteric inhibitor, inhibits incorporation into only one of those peptides. Comparison of the sequences of the labeled tryptic peptides with those of large and small subunits of the enzyme from other species indicate their positions in the primary structure of the spinach enzyme large subunit. The conservation in the amino acid sequences surrounding the lysyl residue in the small subunit and of the lysyl residue in the large subunit in higher plant and in cyanobacterial ADPglucose pyrophosphorylases, which are protected from phosphopyridoxylation by both allosteric effectors, suggests that these lysyl residues are involved in activator binding.

Allosteric Regulation↗
PubMed1994

Structure-function relationships of cyanobacterial ADP-glucose pyrophosphorylase. Site-directed mutagenesis and chemical modification of the activator-binding sites of ADP-glucose pyrophosphorylase from Anabaena PCC 7120.

Chemical modification studies of spinach leaf ADP-glucose pyrophosphorylase with pyridoxal-P have shown that a highly conserved lysyl residue near the C terminus might be involved in the binding of 3-P-glycerate, the allosteric activator. Site-directed mutagenesis of the corresponding residue (Lys419) of the Anabaena enzyme was performed to determine the role of this conserved residue. Replacing Lys419 with either arginine, alanine, glutamine, or glutamic acid produced mutant enzymes with apparent affinities for 3-P-glycerate, 25-150-fold lower than that of the wild-type enzyme. The mutant enzymes, however, were still activated to a great extent at higher concentrations of activator suggesting that an additional site or residue was involved in the binding of the activator. These mutations caused lesser or no effect on the kinetic constants for the substrates and inhibitor, P(i), as well as on the catalytic efficiency and thermal stability. The results suggest that both the charge and size of lysine residue 419 are required for the proper binding of 3-P-glycerate. Chemical modification of the Anabaena wild-type enzyme with pyridoxal-P indicated that Lys419 was the only lysyl residue modified. We further performed the same experiment on the K419R mutant enzyme and found another lysyl residue, Lys382, was modified. Reductive phosphopyridoxylation of the wild-type and K419R enzymes caused dramatic alteration in allosteric properties. The activator, 3-P-glycerate, and inhibitor, P(i), protected the enzyme from reductive phosphopyridoxylation. The modified enzymes were more active in the absence of 3-P-glycerate and less sensitive to P(i) inhibition.

Anabaena↗
PubMed1994

Properties of carbohydrate-free recombinant glycogenin expressed in an Escherichia coli mutant lacking UDP-glucose pyrophosphorylase activity.

Glycogenin, the self-glucosylating primer for glycogen synthesis, is expressed in wild-type E. coli as a recombinant protein in an already partly glucosylated form, owing to the presence of its substrate, UDP-glucose. By using an E. coli mutant strain lacking in UDP-glucose pyrophosphorylase activity, we have succeeded in expressing carbohydrate-free glycogenin (apo-glycogenin) in good yield. When provided with UDPxylose, it autocatalytically adds 1 xylose residue. With UDP-glucose, an average of 8 glucose residues are added. However, release of the self-synthesized maltosaccharide chains with isoamylase reveals them to be a mixture. Chains as long as 11 glucose residues (maltoundecaose) are present. The ability of recombinant apo-glycogenin to self-glucosylate is further proof that a separate enzyme is not needed for the addition of the first glucose residue to Tyr-194 of the protein.

Escherichia coli↗