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At least 721 records · Page 40Linked to original sources
PubMed1990

An NMR study of anion binding to yeast phosphoglycerate kinase.

Anion binding to yeast phosphoglycerate kinase has been investigated using 1H-NMR spectroscopy. The use of anionic paramagnetic probes. [Cr(CN)6]3- and [Fe(CN)6]3-, has enabled the location of the primary anion binding site in the 'basic-patch' region of the amino-terminal domain. The anions interact most closely with Arg-65 and Arg-168. The binding of these and a variety of other anions to this site is directly competitive with the binding of the substrate, 3-phosphoglycerate. Binding of 3-phosphoglycerate and 1.3-bisphosphoglycerate is, however, stronger than expected on the basis of anionic charge and causes conformational changes in the protein not seen with any of the other simple spherical anions investigated. This must be part, at least, of the substrate specificity. Evidence for a secondary anion binding site involving the side chains of surface lysine residues is also presented. It is suggested that the primary anion site is responsible for the observed activation by anions at low concentrations while the secondary site leads to inhibition at higher anion concentrations. The kinetics fit these deductions and a scheme for kinase activity is presented.

Anions↗
PubMed1990

Modelling of substrate binding to 3-phosphoglycerate kinase with analogues of 3-phosphoglycerate.

Two short analogues of 3-phosphoglycerate, -OOC-CHOH-CH2-O-PO32-, phosphonolactate, (-OOC-CHOH-CH2-PO32-) and arsonolactate (-OOC-CHOH-CH2-AsO32-) have been tested with 3-phosphoglycerate kinase. None of these served as substrate for the kinase reaction, unlike the previously studied [Orr, G. A. & Knowles, J. R. (1974) Biochem. J. 141, 721-723] analogues -OOC-CHOH-CH2-CH2-PO32- and -OOC-CHOH-CH2-CH2-AsO32-, which are isosteric with 3-phosphoglycerate. Thus, a decrease in the substrate size and the accompanying stereochemical changes cannot be tolerated by the catalytic mechanism. Instead, both analogues acted as relatively poor competitive inhibitors with respect to both 3-phosphoglycerate and MgATP. AT pH 8.5 and 20 degrees C, the inhibitory constants (Ki) of phosphonolactate and arsnolactate against both substrates are 17 +/- 5 mM and 30 +/- 7 mM, respectively. Surprisingly, however, both analogues proved to be more effective than either 3-phosphoglycerate or its isosteric analogues in protecting the enzyme against modification of its fast-reacting thiols. This comparison suggests that the shorter analogues bind differently, and that the catalytic mechanism demands a precise fitting of the -CH2-O-PO32- segment of the substrate.

Animals↗
PubMed1990

Kinetic misinterpretation of a coupled enzyme reaction can lead to the assumption of an enzyme-enzyme interaction. The example of 3-phospho-D-glycerate kinase and glyceraldehyde-3-phosphate dehydrogenase couple.

The time course of the conversion of 3-phospho-D-glycerate (GriP) to glyceraldehyde-3-phosphate (GraP) catalyzed by 3-phospho-D-glycerate kinase (GriP kinase) and glyceraldehyde-3-phosphate dehydrogenase (GraPDH) couple has been reinvestigated. The dependence of the steady-state rate on the dehydrogenase concentration is fully compatible with the consecutive nature of the reaction and therefore is not necessarily related to a complex formation of the two enzymes. To derive a Kd value of a bienzyme complex, as was done by Sukhodolets et al. [Sukhodolets, M. V., Muronetz, V. I. & Nagradova, N. K. (1987) Biochem. Int. 15, 373-379], is basically erroneous. In contrast with some previous reports, the maximal activity of GriP kinase is not influenced by the auxiliary enzyme present in the coupled assay system. Thus, no special accelerating effect can be attributed to GraPDH. 1,3-Bisphospho-D-glycerate (GriP2) bound to GriP kinase does not seem to be a substrate for GraPDH, providing evidence against channelling of GriP2 between the two enzymes.

Animals↗
PubMed1991

A proton-NMR study of a site-directed mutation (His388----Glu) in the interdomain region of yeast phosphoglycerate kinase. Implications for domain movement.

Proton NMR has been used to study a site-directed mutant of yeast phosphoglycerate kinase in which the interdomain residue His388 has been replaced by a glutamine residue. Using 1H-NMR spectroscopy, it was found that 3-phosphoglycerate binding to the mutant protein induces different conformational effects to those observed for the wild-type enzyme. These differences are not only located at the 3-phosphoglycerate binding site but are also seen as long-range effects at the surface of the protein. Measurements of the Kd for 3-phosphoglycerate from the NMR experiments show that the mutant enzyme has a 30-times reduced affinity for this substrate as compared with the wild-type enzyme. These data are consistent with the suggestion that an aromatic residue at position 388 plays an important role in the proposed hinge-bending mechanism.

Glutamine↗
PubMed1994

Protein organization in the matrix of leaf peroxisomes. A multi-enzyme complex involved in photorespiratory metabolism.

This report is an investigation on how the compartmentation of peroxisomal metabolism, involved in the photorespiratory cycle, is accomplished. With isolated peroxisomes from spinach leaves the conversion of serine to glycerate, as coupled to the conversion of glycolate to glycine, was measured. Not only with intact but also with osmotically shocked peroxisomes, which had retained the aggregated state of the peroxisomal matrix but lost the integrity of the boundary membrane, the rates of glycerate synthesis were as high as required for the photorespiratory cycle in vivo. With both intact and shocked peroxisomes the intermediates glyoxylate and hydroxypyruvate did not equilibrate with the medium. It appears from these results that the apparent compartmentation of peroxisomal metabolism is not due to the function of the boundary membrane but to the organization of peroxisomal enzymes in multi-enzyme complexes. When glycolate was added to peroxisomes without transamination partners, glyoxylate was released from the peroxisomes while the peroxisomal matrix partially disintegrated. With solubilized peroxisomes a partial reconstitution of functional enzyme complexes was achieved by the addition of poly(ethylene glycol). The function of the apparently very stable peroxisomal multi-enzyme complexes in protecting the cells from the toxic intermediates H2O2 and glyoxylate is discussed.

Cell Compartmentation↗
PubMed1995

Determining elasticities from multiple measurements of flux rates and metabolite concentrations. Application of the multiple modulation method to a reconstituted pathway.

A recently developed method to determine elasticities by multiple measurements of steady-state flux rates and metabolite concentrations [Giersch, C. (1994) J. Theor. Biol. 169, 89-99] is applied to a reconstituted metabolic pathway. The pathway is the section of glycolysis converting glycerate-3-phosphate to pyruvate. The elasticities of the pathway enzymes are determined from the dependence on effector concentrations of measured steady-state flux rates and steady-state metabolite concentrations. To verify assumptions regarding the dependence of reaction rates on metabolites, flux control coefficients calculated from enzyme elasticities are compared with those estimated by means of the usual enzyme titration. The proposed method is shown to allow experimental determination of enzyme elasticities but requires, like other experiments in metabolic control analysis, a high level of reproducibility and experimental accuracy which may be difficult to attain.

Glyceric Acids↗
PubMed1988

Ethanol inhibits some of the early effects of epidermal growth factor in vivo.

Charles River male Wistar rats (200-300 g) were meal fed for 9-10 days, injected with either saline, epidermal growth factor (EGF), ethanol, or ethanol combined with EGF and their livers were freeze clamped 5 min after intraperitoneal injection of EGF. Metabolites were measured and the redox state and phosphorylation potential were calculated. Epidermal growth factor alone elevated hepatic content of glucose 1-P, glucose 6-P, fructose 6-P, and 3-phosphoglycerate 1.2-1.3-fold when compared to saline treatment. Ethanol alone decreased hepatic content of 3-phosphoglycerate and phosphoenolpyruvate 3.2-3.7-fold below saline-treated levels. Ethanol, in combination with EGF, decreased hepatic values for 3-phosphoglycerate and phosphoenolpyruvate 2.0-2.3-fold from saline treatment but elevated the content of phosphoenolpyruvate 1.6-fold over ethanol treatment alone. Epidermal growth factor inhibited pyruvate kinase activity 1.3-fold when compared to saline controls but ethanol in the presence of EGF facilitated the recovery of activity of this enzyme.

Animals↗
PubMed2005

Distribution of genes for synthesis of trehalose and Mannosylglycerate in Thermus spp. and direct correlation of these genes with halotolerance.

In this study we correlate the presence of genes leading to the synthesis of trehalose and mannosylglycerate (MG) in 17 strains of the genus Thermus with the ability of the strains to grow and accumulate these compatible solutes in a defined medium containing NaCl. The two sets of genes, namely, otsA/otsB for the synthesis of trehalose and mpgS/mpgP for the synthesis of MG, were necessary for the growth of Thermus thermophilus in a defined medium containing up to 6% NaCl. Strains lacking a complete otsA gene did not grow in defined medium containing >2% NaCl. One strain of T. thermophilus lacking the genes for the synthesis of MG did not grow in a medium with >1% NaCl. We did not identify any of these genes in the type strains of the other seven species of Thermus, and none of those strains grew in defined medium with 1% NaCl. The results strongly indicate that the combined accumulation of trehalose and MG is required for optimal osmotic adjustment.

Base Sequence↗
PubMed2006

Glucosylglycerate biosynthesis in the deepest lineage of the Bacteria: characterization of the thermophilic proteins GpgS and GpgP from Persephonella marina.

The pathway for the synthesis of glucosylglycerate (GG) in the thermophilic bacterium Persephonella marina is proposed based on the activities of recombinant glucosyl-3-phosphoglycerate (GPG) synthase (GpgS) and glucosyl-3-phosphoglycerate phosphatase (GpgP). The sequences of gpgS and gpgP from the cold-adapted bacterium Methanococcoides burtonii were used to identify the homologues in the genome of P. marina, which were separately cloned and overexpressed as His-tagged proteins in Escherichia coli. The recombinant GpgS protein of P. marina, unlike the homologue from M. burtonii, which was specific for GDP-glucose, catalyzed the synthesis of GPG from UDP-glucose, GDP-glucose, ADP-glucose, and TDP-glucose (in order of decreasing efficiency) and from d-3-phosphoglycerate, with maximal activity at 90 degrees C. The recombinant GpgP protein, like the M. burtonii homologue, dephosphorylated GPG and mannosyl-3-phosphoglycerate (MPG) to GG and mannosylglycerate, respectively, yet at high temperatures the hydrolysis of GPG was more efficient than that of MPG. Gel filtration indicates that GpgS is a dimeric protein, while GpgP is monomeric. This is the first characterization of genes and enzymes for the synthesis of GG in a thermophile.

Bacteria↗
PubMed1975

Growth of Pseudomonas C on C1 compounds: enzyme activites in extracts of Pseudomonas C cells grown on methanol, formaldehyde, and formate as sole carbon sources.

Pseudomonas C can grow on methanol, formaldehyde, or formate as sole carbon source. It is proposed that the assimilation of carbon by Pseudomonas C grown on different C1 growth substrates proceeds via one of two metabolic pathways, the serine pathway or the allulose pathway (the ribose phosphate cycle of formaldehyde fixation). This contention is based on the distribution of two key enzymes, each of which appears to be specifically involved in one of the assimilation pathways, glycerate dehydrogenase (serine pathway) and hexose phosphate synthetase (allulose pathway). The assimilation of methanol in Pseudomonas C cells appears to occur via the allulose pathway, whereas the utilization of formaldehyde or formate in cells grown on formaldehyde or formate as sole carbon sources appears by the serine pathway. When methanol is present together with formaldehyde or formate in the growth medium, the formaldehyde or formate is utilized by the allulose pathway.

Alcohol Oxidoreductases↗
PubMed1977

Phosphoenolpyruvate and 2-phosphoglycerate: endogenous energy source(s) for sugar accumulation by starved cells of Streptococcus lactis.

In the absence of an exogenous energy source, galactose-grown cells of Streptococcus lactis ML3 rapidly accumulated thiomethyl-beta-D-galactopyranoside (TMG) and 2-deoxyglucose to intracellular concentrations of 40 to 50 mM. Starved cells maintained the capacity for TMG uptake for many hours, and accumulation of the beta-galactoside was insensitive to proton-conducting ionophores (tetrachlorosalicylanilide and carbonylcyanide-m-chlorophenyl hydrazone) and sulfydryl group reagents including iodoacetate and N-ethylmaleimide. Fluorimetric analysis of glycolytic intermediates in extracts prepared from starved cells revealed (a) high intracellular levels of phosphoenolpyruvate (13 mM; PEP) and 2-phosphoglycerate (approximately 39 mM; 2-PG), but an absence of other metabolites including glucose 6-phosphate, fructose 6-phosphate, fructose 1,6-diphosphate, and triosephosphates. The following criteria showed PEP (and 2-PG) to be the endogenous energy source for TMG accumulation by the phosphotransferase system: the intracellular concentrations of PEP and 2-PG decreased with concomitant uptake of TMG, and a close correlation was observed between maximum accumulation of the beta-galactoside and the total available concentration of the two intermediates; TMG accumulated as an anionic derivative, which after extraction and incubation with alkaline phosphatase (EC 3.1.3.1) formed the original analogue; fluoride inhibition of 2-phospho-D-glycerate hydrolyase (EC 4.2.1.11) prevented the conversion of 2-PG to PEP, and uptake of TMG by the starved cells was reduced by 80%; and the stoichiometric ratio [TMG] accumulated/[PEP] consumed was almost unity (0.93). In cells metabolizing glucose, all intermediates listed in (a) and (b) were found. Upon exhaustion of glucose from the medium, the metabolites in (b) were not longer detectable, while the intracellular concentrations of PEP and 2-PG increased to the levels previously observed in starved cells. The glycolytic intermediates in (b) are all in vitro heterotropic effectors of pyruvate kinase (adenosine 5'-triphosphate:pyruvate 2-O-phosphotransferase, EC 2.7.1.40) from S. lactis ML3. It is suggested that the capacity of starved cells to maintain high intracellular concentrations of PEP and 2-PG is a consequence of decreased in vivo activity of this key regulatory enzyme of glycolysis.

Biological Transport↗
PubMed1980

Regulation of carbohydrate transport activities in Salmonella typhimurium: use of the phosphoglycerate transport system to energize solute uptake.

The phosphoglycerate transport system was employed to supply energy-depleted, lysozyme-treated Salmonella typhimurium cells with a continuous intracellular source of phosphoenolpyruvate. When the cells had been induced to high levels of the phosphoglycerate transport system, a low extracellular concentration of phosphoenolpyruvate (0.1 mM) half maximally stimulated uptake of methyl alpha-glucoside via the phosphoenolpyruvate:sugar phosphotransferase system. If the phosphoglycerate transport system was not induced before energy depletion, 100 times this concentration of phosphoenolpyruvate was required for half-maximal stimulation. Phosphoenolpyruvate could not be replaced by other energy sources if potassium fluoride (an inhibitor of enolase) was present. Inhibition of [14C]-glycerol uptake into energy-depleted cells by methyl alpha-glucoside was demonstrated. A concentration of phosphoenolpyruvate which stimulated methyl alpha-glucoside accumulation counteracted the inhibitory effect of the glucoside. In the presence of potassium fluoride, phosphoenolpyruvate could not be replaced by other energy sources. Inhibition of glycerol uptake by methyl alpha-glucoside in intact untreated cells was also counteracted by phosphoenolpyruvate, but several energy sources were equally effective; potassium fluoride was without effect. These and other results were interpreted in terms of a mechanism in which the relative proportions of the phosphorylated and nonphosphorylated forms of a cell constituent influence the activity of the glycerol transport system.

Biological Transport, Active↗
PubMed1988

Effect of a mutation preventing lipid modification on localization of the pCloDF13-encoded bacteriocin release protein and on release of cloacin DF13.

The pCloDF13-encoded bacteriocin release protein (BRP; Mr 2,871) is essential for the translocation of cloacin DF13 across the cell envelope of producing Escherichia coli cells. Overproduction of this BRP provokes lysis (quasilysis) of cells. Construction and analysis of a hybrid BRP-beta-lactamase protein (BRP-Bla) demonstrated that the BRP contains a lipid modified cysteine residue at its amino terminus and is mainly located in the outer membrane. The significance of lipid modification for the localization and functioning of the BRP was investigated. Site-directed mutagenesis was used to substitute the cysteine residue for a glycine residue in the lipobox of the BRP and the BRP-Bla protein. The mutated BRP was unable to bring about the release of cloacin DF13 and could not provide the lysis (quasilysis) of host cells. However, the mutated BRP strongly inhibited the colony-forming ability of the cells, indicating that induction of the mutated protein still affected cell viability. In contrast to the wild-type BRP-Bla protein, the mutated BRP-Bla protein was mainly located in the cytoplasmic membrane, indicating that the mutation prevented the proper localization of the protein. The results indicated that lipid modification of the BRP is required for its localization and release of cloacin DF13, but not for its lethality to host cells.

Bacterial Proteins↗