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PubMed1988

Oxidative degradation of glucose adducts to protein. Formation of 3-(N epsilon-lysino)-lactic acid from model compounds and glycated proteins.

The chemistry of Maillard or browning reactions of glycated proteins is being studied in model systems in vitro in order to characterize potential reaction pathways and products in biological systems. In previous work with the Amadori rearrangement product N alpha-formyl-N epsilon-fructoselysine (fFL), an analog of glycated lysine residues in proteins, we showed that fFL was oxidatively cleaved between C-2 and C-3 of the carbohydrate chain to yield N epsilon-carboxymethyllysine (CML) and D-erythronic acid. We then detected CML in proteins glycated in vitro, as well as in human lens proteins and collagen in vivo (Ahmed, M. U., Thorpe, S. R., and Baynes, J. W. (1986) J. Biol. Chem. 261, 4889-4894). This work provided an explanation for the origin of CML in human urine and evidence for non-browning pathways of the Maillard reaction in vivo. In this report we describe the identification of a second set of products resulting from oxidative cleavage of fFL between C-3 and C-4 of the sugar chain, i.e. 3-(N epsilon-lysino)-lactic acid (LL) and D-glyceric acid. The formation of LL from fFL was increased at slightly acid pH, representing about 30% of the yield of CML at pH 6.4, compared with 4% at pH 7.4 in phosphate buffer. By gas chromatography-mass spectroscopy, LL was detected in proteins glycated in vitro and then identified as a natural product in human lens proteins and urine. Our results indicate that oxidative degradation of Amadori adducts to proteins occurs in vivo, leading to formation and excretion of CML and LL. These non-browning pathways for reaction of Amadori compounds may be physiologically relevant mechanisms for averting potentially damaging consequences of the Maillard reaction.

Chemical Phenomena↗
PubMed1992

Peptide secondary structure induced by a micellar phospholipidic interface: proton NMR conformational study of a lipopeptide.

The conformational change of the model peptide Ac-K-G-R-G-D-G-amide induced by a phospholipidic interface was investigated by proton nuclear magnetic resonance (1H NMR). In aqueous solution, the free peptide is highly flexible and disordered, even in the presence of deuterated dodecyl-phosphocholine (DPC-d38) micelles which mimic a membrane interface. The lipopeptide, obtained by grafting a lipid anchor [2,3-dipalmitoyl-D-(+)-glyceric acid] to the lysine side chain of the peptide, was studied by standard 2D 1H NMR spectroscopy combined with distance geometry and simulated annealing calculations. When anchored to a micelle interface, the peptide acquires a definite turn (II/I') conformation. We were also able to describe precisely the conformation of the diacylglyceric fragment of the lipopeptide in a lipid environment and to establish the average orientation of the peptide segment with respect to the micelle surface.

Amino Acid Sequence↗
PubMed1990

Structural and stereoisomeric specificity of serum-borne sugar acids related to feeding control by rats.

Specificity of chemical structures and stereoisomers among serum-borne short-chain organic acids in rats were assessed for their effects on feeding behavior and humoral factors by infusion into the rat third cerebroventricle. Infusion of glyceric acid (1.0 mumol), 3,4-dihydroxybutanoic acid gamma-lactone (3,4-DB) or 3,4,5-trihydroxypentanoic acid gamma-lactone (2.50 mumol) immediately before the dark phase decreased food intake for, at most, 24 h. These acids did not significantly affect drinking or ambulation. Initial feeding, not necessarily accompanied by periprandial drinking, was induced after infusion of 2,4-dihydroxybutanoic acid gamma-lactone, 2,4,5-trihydroxypentanoic acid gamma-lactone (2,4,5-TP) or exogenous 2,4,5,6-tetrahydroxyhexanoic acid gamma-lactone (2.50 mumol) in the light phase. Of these acids, 3,4-DB most potently suppressed and 2,4,5-TP most potently enhanced feeding. Of these, the 2S,4S-isomer and the 3S-isomer were the most potent of 2,4,5-TP and 3,4-DB, respectively. Only the 2S,4S-isomer of 2,4,5-TP induced hypoglycemia with hyperinsulinemia, whereas opposite effects were produced by the 3S-isomer of 3,4-DB. The results indicate that the positions of the hydroxyl groups on 4-butanolide and the S- and S,S-stereoisomers are important in modulating food intake through the hypothalamus.

Animals↗
PubMed1976

D-Glyceric acidemia in a patient with chronic metabolic acidosis.

A patient is described with glyceric acidemia and glyceric aciduria. The main clinical problems in infancy were severe metabolic acidosis and failure to thrive. The patient needs permanent treatment with bicarbonate. Hyperglycinemia, as described in the first case discovered elsewhere, was not present. The glyceric acid was found to have the D-configuration, as analyzed by capillary gas chromatography of its di-O-acetyl-l-menthyl ester. The abnormality may result from a defect in serine metabolism.

Acidosis↗
PubMed1999

Structural studies on a 2,3-diphosphoglycerate independent phosphoglycerate mutase from Bacillus stearothermophilus.

Phosphoglycerate mutase (PGM), an important enzyme in the glycolytic pathway, catalyzes the transfer of a phosphate group between the 2 and the 3 positions of glyceric acid. The gene coding for the 2, 3-diphosphoglycerate independent monomeric PGM from Bacillus stearothermophilus (57 kDa), whose activity is extremely pH sensitive and has an absolute and specific requirement for Mn2+, has been cloned and the enzyme overexpressed and purified to homogeneity. Circular dichroism studies showed at most only small secondary structure changes in the enzyme upon binding to Mn2+ or its 3-phosphoglycerate substrate, but thermal unfolding analyses revealed that Mn2+ but not 3-phosphoglycerate caused a large increase in the enzyme's stability. Diffraction-quality crystals of the enzyme were obtained at neutral pH in the presence of 3-phosphoglyceric acid with ammonium sulfate as the precipitating agent; these crystals diffract X rays to beyond 2.5-A resolution and belong to the orthorhombic space group C2221 with unit cell dimensions, a = 58.42, b = 206.08, c = 124.87 A, and alpha = beta = gamma = 90.0 degrees. The selenomethionyl version of the B. stearothermophilus protein has also been overexpressed, purified, and crystallized. Employing these crystals, the determination of the three-dimensional structure of this PGM by the multiwavelength anomalous dispersion method is in progress.

2,3-Diphosphoglycerate↗
PubMed2004

Avidin self-associates with boric acid gel suspensions: an affinity boron carrier that might be developed for boron neutron-capture therapy.

It has been shown in preliminary studies that the antibacterial protein avidin self-associates with the boric acid gel polymer, and avidin-coated gel particles in the micrometer and submicrometer size ranges are of interest for boron neutron-capture therapy (BNCT), which is neutron-induced fission of boron-10 to produce intense alpha radiation for tumor destruction. The gel particles carry large amounts of boron-10 and are theoretically able effect a meaningful tissue dosing through BNCT. A gross precipitation of gel particles occurs within 46 min of mixing when the avidin/colloid ratio is about 0.34 g avidin/g colloid. This is a minimum time if gel and avidin concentrations are in the low microgram/milliliter range, but at higher proportions of avidin the time delay to precipitation increases significantly; i.e., the colloid surface becomes blocked, inhibiting lattice formation. The avidin-coated gel particles eventually cross-link, forming a solid matrix and precipitating on a timescale measured on the order of an hour. At shorter exposure times rapid agglutination-like reactions were observed with biotinylated bovine albumin, suggesting that two-stage pretargeting of specific tissues should be possible with biotinylated antitumor antibodies. However, for BNCT to be practical, avidin's interaction with the gel needs to be strengthened, and all aryl-B(OH)(2) groups on the particle surfaces must be blocked, or else the particles will interact strongly and nonspecifically with each other and with the carbohydrate groups present on most cell surfaces. Glyceric acid delays the precipitation of the particle suspensions while most simple and complex carbohydrates accelerate it.

Albumins↗
PubMed1998

Kinetics and mechanism of oxidation of erythro-series pentoses and hexoses by N-chloro-p-toluenesulfonamide.

The kinetics and mechanism of oxidation of D-glucose, D-mannose, D-fructose, D-arabinose, and D-ribose with chloramine-T in alkaline medium were studied. The rate law, rate = k [Chloramine-T] [Sugar] [HO-]2, was observed. The rate of the reaction was influenced by a change in ionic strength of the medium, and the dielectric effect was found to be negative. The latter enabled the computation of dAB, the size of the activated complex. The reaction rate was almost doubled in deuterium oxide. Activation energies were calculated from the Arrhenius plots. HPLC and GLC-MS analyses of the products indicated that the sugars were oxidized to a mixture of aldonic acids, consisting of arabinonic, ribonic, erythronic, and glyceric acids. Based on these data, a plausible mechanism involving the aldo-enolic anions of pentoses and keto-enolic anions of hexoses is suggested.

Chemical Phenomena↗
PubMed1990

D(+)-glyceric aciduria: etiology and clinical consequences.

A family comprising mother, father, and five children is described. Four of the children were found to excrete massive amounts of D(+)-glyceric acid in their urine. This was verified by gas chromatography-mass spectrometry and the configuration determined by capillary gas chromatography of O-acetylated menthyl esters. The excretion ranged from 10.8 to 19.9 mmol/24 h. The remaining child and the parents showed no evidence of this unusual metabolite. The virtual absence of clinical manifestations in this family was particularly interesting. Only two of the children showed any clinical abnormality and this was limited to mild microcephaly and speech delay; the other two children found to excrete large amounts of D(+)-glycerate were healthy and developmentally normal at 7 y and 9 y of age. There was a marked increase in the excretion rate of D(+)-glycerate in response to both oral fructose and serine loading. These results are consistent with a deficiency of D(+)-glycerate kinase and indicate the potentially benign nature of this disorder.

Administration, Oral↗
PubMed1969

The metabolism of D-glyceraldehyde by the lens.

1. The metabolism of d-glyceraldehyde by the lens was examined. 2. When low concentrations of d-[U-(14)C]glyceraldehyde were incubated with lens extracts there was no incorporation of the label into protein; more than two-thirds of the labelled metabolites consisted of glyceric acid and glycerol, their relative proportions depending on the species. Lactic acid, a phosphate, glutathione-glyceraldehyde compounds and a neutral compound were also formed. 3. When high concentrations of d-[U-(14)C]glyceraldehyde were incubated with lens, extensive incorporation of the label into protein occurred and the protein became yellow-brown. This coloured protein did not exhibit the fluorescent properties shown by the brown proteins of human cataractous senile lens, or of naphthaquinone-treated lens. 4. Evidence that d-glyceraldehyde is formed by the lens was sought but not found.

Animals↗
PubMed1998

Tissue spaces in rat heart, liver, and skeletal muscle in vivo.

Tissue spaces were determined in rat heart, liver, and skeletal muscle in vivo using isotopically labeled [14C]inulin. Tracer was injected into the jugular vein of pentobarbital-anesthetized male Sprague-Dawley rats. After a 30-min equilibration period, a blood sample was taken, and heart, liver, and gastrocnemius muscle were excised and immediately freeze clamped at liquid nitrogen temperatures. The extracellular inulin space was 0.209 +/- 0.006 (n = 13), 0.203 +/- 0.080 (n = 7), and 0.124 +/- 0.006 (SE) ml/g wet wt tissue (n = 8) for heart, liver, and skeletal muscle, respectively. Total tissue water was 0.791 +/- 0.005 (n = 9), 0.732 +/- 0.002 (n = 9), and 0.755 +/- 0.005 ml/g wet wt tissue (n = 10) for heart, liver, and skeletal muscle, respectively. Expressed as a percentage of total tissue water, the intracellular space was 73.6, 72.2, and 83. 7% for heart, liver, and skeletal muscle, respectively. With use of 2,3-diphospho-D-glyceric acid as a vascular marker, the interstitial space was calculated by subtracting the counts in tissue due to whole blood from total tissue counts and dividing by plasma counts. The interstitial space was 18.8, 22.4, and 14.5% of total tissue water, with accompanying plasma spaces of 7.7, 5.3, and 1.8% for heart, liver, and gastrocnemius muscle, respectively. The tracer method used in this study provides a quantitative assessment of water distribution in tissues of nonnephrectomized rats that has applications for calculation of tissue ion and metabolite concentrations, gradients, and fluxes under normal and pathophysiological conditions.

Animals↗
PubMed1995

New hydrophilic polyesters and related polymers as bioerodible polymeric matrices.

A survey is reported on our activity performed in the last few years on the preparation of new synthetic and semisynthetic polymeric materials endowed with bioerodible-biodegradable characteristics and designed for applications in the practice of controlled release of active principles of pharmaceutical and agrochemical significance. The presentation of the results will be arranged into the following sections: (1) hydroxyl containing polyesters, that comprise polymerization products based on racemic and optically active glyceric acid, or attained by polyaddition reactions among cyclic anhydrides, including also carbon dioxide, with monoglycidyl ethers of reversibly protected polyols. In this class are also presented the related polyhydroxylated systems obtained by selective grafting functional epoxides on cyclodextrins. (2) Bioerodible carboxyl containing polymeric systems as derived from the alternating copolymerization of maleic anhydride with alkyl vinyl ethers followed by partial esterification of maleic anhydride groups. (3) Linear and cross-linked functional polymers of synthetic and semisynthetic origin with hydrogel forming capability. Typical examples of their applications in the release of drugs and phytodrugs are also presented.

Biodegradation, Environmental↗
PubMed1975

Carbohydrate metabolism and its response to catecholamines as modified in alkalotic rat.

Metabolic activities and their responses to catecholamines were studied in fasted rats exposed to simulated altitudes. Analysis of hepatic levels of gluconeogenic intermediates revealed the inhibition of gluconeogenesis between glyceric acid 3-P and fructose 6-P associated with a rise of the ratios of redox pairs such as lactate to pyruvate in livers of alkalotic rats. Inhibition of gluconeogenesis was indicated also by the suppressed incorporation of glutamate 14C into blood glucose. Since no activation was detected on glycolytic pathway of skeletal muscles, marked hyperlactacidemia during alkalosis appeared to result from the suppression of hepatic gluconeogenesis. Most of metabolic actions of epinephrine and isoproterenal known to be mediated via the beta receptor were significantly reduced but not completely abolished during alkalosis. Exceptionally, hyperinsulinemia induced by isoproterenol was completely reversed and replaced by hypoinsulinemia during alkalosis. Despite hypoinsulinemia, hyperglycemia induced by glucose load decreased more rapidly in alkalotic than in normal rats. In view of the fact that the adrenergic alpha receptor is involved in theinhibition of insulin secretion, the observed irregular modifications of catecholamine actions could be explained on the basis of a postulate that the adrenergic alpha-receptor functions are potentiated in alkalosis.

Alkalosis, Respiratory↗
PubMed1987

Photorespiration stoichiometry in leaves estimated by combined physical and stereochemical methods: allowance for isomerase-catalyzed 3H losses in ribulose bisphosphate regeneration.

We showed previously [K.R. Hanson and R.B. Peterson (1986) Arch. Biochem. Biophys. 246, 332-346] that under steady-state photosynthetic conditions the fraction of ribulose bisphosphate oxidized and the fraction of glycolate carbon photorespired (the stoichiometry of photorespiration) may be estimated in leaves by a combination of physical and stereochemical methods. The calculations assumed that when (3R)-D-[3-3H1,3-14C]glyceric acid is supplied to illuminated leaf discs the only loss of 3H from the combined photosynthetic and photorespiratory system is the result of glycolate oxidase action; i.e., the isomerase-catalyzed losses in the regeneration of ribulose bisphosphate are negligible. The present study of tobacco leaf discs under zero-photorespiration conditions (low O2 and high CO2 concentrations), and also of maize leaf discs, shows that some 3H losses occur (between 8 and 13% of the 3H at C-1 of ribulose 5-phosphate). The calculated loss varied moderately with temperature but did not vary when the flux of ribulose bisphosphate formation was altered by changing the irradiance. The calculated loss under zero-photorespiration conditions, therefore, may be used to calculate ribulose bisphosphate and glycolate partitioning under other conditions. Earlier experiments on the influence of O2 and CO2 concentrations of temperature on the partitioning of ribulose bisphosphate and glycolate have been reexamined. The loss corrections decreased all values for the fraction of ribulose bisphosphate oxidized and increased all values for the stoichiometry of photorespiration. Essentially all stoichiometry values were above the theoretical lower limit of 25%. The previous conclusion that the stoichiometry of photorespiration substantially exceeds 25% at higher O2 concentrations and higher temperatures is unchanged. The results with maize leaf discs implied that there is very little oxidation of ribulose 1,5-bisphosphate under normal-air conditions; i.e., photorespiration is indeed suppressed, not merely hidden, by efficient refixation of CO2.

Carbon Dioxide↗
PubMed1974

Calorimetric studies of the role of magnesium ions in yeast enolase catalysis.

The binding of magnesium ions and of the competitive inhibitor 3-phospho-D-glyceric acid to yeast enolase (2-phospho-D-glycerate hydrolyase, EC 4.2.1.11) has been studied calorimetrically. Thermal titration of the apoprotein with magnesium ions provides evidence that two magnesium ions bind immeasurably tightly to the dimeric enzyme, either anticooperatively to interacting sites or to two independent, nonidentical sites. Measurements of the saturation heat in buffers with different enthalpies of protonation are consistent with the release of two protons when the metal-binding sites are filled at pH 7.5. The enthalpy of binding of the two magnesium ions, corrected for the release of two protons, is +11.7 kcal (+49.0 kJ) per mole of dimeric protein. Thermal titration of the magnesium-saturated enzyme with 3-phosphoglyceric acid corroborates the conclusion of Spring and Wold [Biochemistry (1971) 10, 4655-4660] that the enolase dimer possesses two equivalent and independent substrate-binding sites. The dissociation constant for the enzyme-inhibitor complex calculated from the thermal data is 2 mM. The thermal studies of 3-phosphoglyceric acid binding also confirm that metal ions are required for substrate binding and that substrate binds at the two specific metal-binding sites on the apoprotein. Experiments in buffers with different enthalpies of ionization provide evidence for proton uptake when 3-phosphoglyceric acid is bound.

Apoproteins↗
PubMed1976

D-glyceric acidemia: biohcemical studies of a new syndrome.

Studies of a mentally retarded boy, clinically suffering from nonketotic hyperglycinemia, are reported. Using combined gas chromatography-mass spectrometry, enzyme specificity studies, and spectropolariometry D-glyceric acid in extremely elevated concentrations was demonstrated in both serum and urine (serum: 1.0-1.3 mmol/liter, urine: 33-187 mmol/liter). Hydroxypyruvic acid was not detectable in urine from this boy using a gas chromatographic method with a limit of detection of 0.3 mmol/liter. Enzyme assays of D-glyceric dehydrogenase on blood leukocytes demonstrated significantly lower activity in the patient compared with five normal children.

Alcohol Oxidoreductases↗
PubMed1977

Gas chromatographic and mass spectrometric studies on urinary organic acids in a patient with congenital lactic acidosis due to pyruvate decarboxylase deficiency.

Detailed studies, using gas chromatography and mass spectrometric methods, of the urinary organic acids excreted by a patient with proven pyruvate decarboxylase deficiency are reported. In addition to the greatly-increased levels of lactate and pyruvate, marked elevation in the levels of 2-oxoglutaric, malic, and isocitric acids were observed, with associated increases 2-hydroxyglutaric, fumaric, succinic, and glyceric acids, and reduced citric acid excretion. The levels of excretion during clinically static and acute periods are compared to those in a normal neonate and normal infants. The metabolites observed indicate a probable defect in the oxidation of pyruvate by pyruvate dehydrogenase and suggest the presence of secondary defects in the tricarboxylic acid cycle. Studies of this type may enable the relatively rapid identification of the probable underlying enzyme deficiency in cases of congenital lactic acidosis, prior to confirmatory enzyme studies.

Acidosis↗
PubMed1977

Organic acid and potassium accumulation in guard cells during stomatal opening.

Leaflets of Vicia faba L. with either open or closed stomata were quick-frozen and freeze-dried. Individual guard cell pairs and pure samples of palisade parenchyma, spongy parenchyma, and epidermis lacking guard cells were dissected from the leaflets, weighed, and assayed for organic acids or K(+).K(+) was measured by a new enzymatic method. In guard cells of open stomata, as compared to closed stomata, K(+) was 2- to 4-fold higher, malic acid 6-fold higher, and citric acid 3-fold higher. Both aspartic and glutamic acids were also higher, but the amounts present were low compared to malic and citric acids. Isocitric acid was significantly higher in one experiment, but not in another. Glyceric acid was not increased. Succinic acid was too low to detect by the method used; but in guard cells of open stomata the concentration must have been less than 2% of that of malic acid. Malic acid was higher in the palisade parenchyma from the leaflet with open stomata. The ion balance shows that malic and citric acids provide much of the counter ion for the K(+) taken up during stomatal opening.

Journal Article↗
PubMed1995

Cyanopeptolin S, a sulfate-containing depsipeptide from a water bloom of Microcystis sp.

A new sulfated, cyclic depsipeptide, called cyanopeptolin S, from Microcystis sp. was isolated from a water bloom in the Auensee/Leipzig (Germany). The depsipeptide had a relative molecular mass of 925 and contained L-arginine, L-threonine, L-isoleucine, N-methyl-L-phenylalanine, a L-glutamic acid-delta-aldehyde ring system and a sulfated D-configurated glyceric acid as a side chain. The structure was elucidated by means of two-dimensional 1H and 13C nuclear magnetic resonance spectroscopy, fast atom bombardment mass spectroscopy. Fourier transformed infrared spectroscopy and combined gas-liquid chromatography/mass spectrometry. Cyanopeptolin S inhibited trypsin with an IC50 < or = 0.2 micrograms ml-1.

Bacterial Proteins↗