Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. The effect of acute alterations of plasma sodium concentration (PNa) on renal sodium excretion (UNaV) was investigated by three types of experiments on anaesthetized dogs: (a) A local increase in PNa at one kidney was produced by infusion of hypertonic saline directly into its artery while systemic levels of PNa were stabilized by haemodialysis. (b) Systemic levels of PNa were lowered by exchange transfusion of blood for an equal volume of salt-free dextran-in-dextrose solution. The results were contrasted with those observed after similar exchanges, but using dextran-in-saline solution. (c) The level of PNa was altered by varying the sodium concentration of a saline solution infused at a fixed rate either intravenously or into one renal artery. 2. All three types of experiment suggest a dependence of UNaV on PNa Analysis demonstrated that this relationship was not due to contemporary changes in: packed cell volume; plasma solids concentration; plasma potassium concentration; blood pressure or plasma hydrogen ion concentration. The distribution of these variables did not change with PNa except for plasma hydrogen ion concentration. Moreover, the relationship persisted when data were selected to exclude clearance periods in which the value for any variable had shifted past the group mean obtained before PNa was altered. 3. The fall in UNaV at low levels of PNa could be attributed to a fall in glomerular filtration rate (GFR), but the progressive rise in UNaV seen as PNa exceeded 150 m-mole 1(-1) occurred despite a fall in GFR and no apparent change in the mean filtered load of sodium. These results suggest that the increased sodium excretion accompanying raised levels of PNa is due to reduced tubular re-absorption of sodium.
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PMID:Plasma sodium concentration and sodium excretion in the anaesthetized dog. 0 71

Michaelis-Menten kinetics are observed in studies of highly purified bovine adrenal glucose-6-phosphate dehydrogenase at pH8.0 in 0.1 M bicine. The Km for NADP+ is 3.8 muM and for glucose-6-phosphate, 61 muM. At pH 6.9 Km for NADP+ increases to 6.5 muM. The enzyme is inhibited by NADPH both at pH 6.8 and at 8.0 with a Kip of 2.36 muM at pH 8.0. Inhibition is competitive with respect to both substrates implying that addition of substrates is random ordered. The data are also interpreted in terms of "reducing charge", the mole fraction of coenzyme in the reduced form. This appears to be the major mechanism for regulation of the pentose shunt. D-glucose, oxidized by the enzyme at a very slow rate, is also a competitive inhibitor for the natural substrate with a Ki of 0.29 M. Phosphate is a competitive inhibitor for glucose-6-phosphate oxidation but both phosphate and sulfate accelerate glucose oxidation suggesting a common binding site for the two anions and the phosphate of the natural substrate. While binding of ACTH to our enzyme preparations has been observed, we have not been able, in spite of repeated attempts, to demonstrate augmentation of the activity of the enzyme by the addition of ACTH.
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PMID:Kinetics and control of bovine adrenal glucose-6-phosphate dehydrogenase. 0 67

Indoleamine 2,3-dioxygenase was purified from rabbit small intestine to apparent homogeneity as judged by polyacrylamide gel electrophoresis and analytical ultracentrifugation. The native enzyme was a monomeric protein of a molecular weight of 41,000 +/- 1,000 with an s020,w value of 3.45 S. It had a relative abundance of hydrophobic amino acids such as valine, leucine, and isoleucine, and contained approximately 5% carbohydrate by weight. The estimated content of sugar residues per mol of enzyme was: galactose, 1.2; mannose, 2.6; N-acetylglucosamine, 5.2; and sialic acid, 0.8. One mole of enzyme had 0.8 mol of protoheme IX as a prosthetic group. However, copper was not detected in a significant amount and the ratio of copper to heme was less than 0.03. EPR spectra of the nitric oxide complex of the ferrous enzyme indicated that a nitrogen atom, possibly in an imidazole group, might be coordinated as the fifth ligand of the heme coenzyme. The anisotropic g values were gx = 2.08, gy = 1.98, and gz = 2.01. A single enzyme protein catalyzed the oxygenative ring cleavage of D- and L-tryptophan, D- and L-5-hydroxytryptophan, tryptamine, and serotonin. In addition, the purified enzyme had a peroxidase activity with guaiacol and potassium iodide as hydrogen donors, but not a catalase activity.
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PMID:Indoleamine 2,3-dioxygenase. Purification and some properties. 2 87

The initial rates of transport of uridine, thymidien, purines, choline and 2-deoxy-D-glucose by cultured Novikoff rat hepatoma cells were determined as a function of temperature between 5 and 41 degrees C. Arrhenius plots of all transport systems exhibited sharp breaks in slope; between 17 and 23 degrees for uridine, thymidine and hypoxanthine-guanine transport and between 29 and 32 degrees for choline and 2-deoxy-D-glucose transport. The activation energies for the transport systems changed from 15-26 kcal/mole below the transition temperatures to 4-9 kcal/mole above the transition temperatures. Propagation of the cells in the presence of cis-6-octadecenoic acid which results in marked changes in the lipid composition of cell membrane, had little effect on the temperature characteristics of the various transport systems. Similarly, propagation of the cells for 24 hr in media containing Tween 40 or nystatin had no effect on the capacity of the cells to transport the various substrates or on the temperature dependence of the transport systems. The presence of ethanol, phenethyl alcohol or Persantin at concentrations that inhibited thymidine and 2-deoxy-D-glucose transport between 40 and 70% also did not alter the transition temperatures or activation energies for the transport of these substrates. Cytochalasin B, on the other hand, shifted the transition temperature for 2-deoxy-D-glucose transport to higher temperatures in a concentration-dependent manner, whereas it had no effect on the temperature dependence of thymidien transport.
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PMID:Temperature-dependent changes in activation energies of the transport systems for nucleosides, choline and deoxyglucose of cultured Novikoff rat hepatoma cells and effects of cytochalasin B and lipid solvents. 5 43

Angiotensin-converting enzyme has been solubilized from a particulate fraction of rabbit lung and purified to apparent homogeneity in 11% yield by a procedure including fractionation with DEAE-cellulose and calcium phosphate gel, elution from Sephadex G-200, and lectin affinity chromatography. The molecular weight estimated by equilibrium sedimentation was approximately 129,000, either in the absence or presence of 6 M guanidine hydrochloride. A slightly higher value of 140,000 determined for the reduced, denatured protein by gel electrophoresis in the presence of sodium dodecyl sulfate and a much higher figure derived from gel filtration are probably due to the glycoprotein nature of the enzyme. Its oligosaccharide content accounted for 26% of the weight calculated from its amino acid and carbohydrate composition. The estimated content of sugar residues per mole was: galactose, 57; N-acetylglucosamine, 53; mannose, 43; N-acetylneuraminic acid, 19; and fucose, 4. Threonine and alanine were identified, respectively, as NH2-terminal and COOH-terminal residues by the dansylation procedure and by digestion with carboxypeptidase A. The enzyme was found to contain approximately 1 g atom of zinc per mol. Km values for hydrolysis of hippurylhistidylleucine and angiotensin I were 2.3 and 0.07 mM, and the corresponding turnover numbers were 15,430 and 792 mol/min/mol at 37 degrees. Bradykinin was also a substrate, and release of its COOH-terminal dipeptide, Phe-Arg, was catalyzed at a comparable rate to that of His-Leu from the COOH terminus of angiotensin I. Enzyme activity required the presence of chloride ions and was inhibited by EDTA and by low concentrations of Bothrops bradykinin-potentiating peptides. In addition, hydrolysis of hippurylhistidylleucine was inhibited competitively by other defined peptides, including di- and tripeptides, which were not substrates.
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PMID:Pulmonary angiotensin-converting enzyme. Structural and catalytic properties. 16 57

Human serum low density lipoprotein (d = 1.027-1.045) was delipidated with organic solvents and the apoprotein digested with thermolysin. The digest was fractionated by gel filtration and DEAE-cellulose chromatography. Two glycopeptides were obtained. One of the glycopeptides (GP-I) contained 2 residues of N-acetylglucosamine and 6 residues of mannose per mole of the glycopeptide, while the other contained 2 sialic acid, 5 mannose, 2 galactose, and 3 N-acetylglucosamine residues per mole of glycopeptide. The results of sequential enzymatic digestion with purified glycosidases, periodate oxidation, and partial acid hydrolysis lead us to propose the following sturctures for the two glycopeptides: (see article). These glycopeptides represent at least 50% of the carbohydrate moiety of LDL.
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PMID:The monosaccharide composition and sequence of the carbohydrate moiety of human serum low density lipoproteins. 17 43

One neutral and two acidic glycoasparagines were isolated from the urine of patients with aspartylglycosylaminuria (AGU). The neutral one was identified as beta-Gal-(1 leads to 4)-beta-GlcNAc-Asn. The acidic ones were composed of 1 mole of sialic acid and 2 moles each of galactose and N-acetylglucosamine, attached to asparagine, and were isomeric with respect to the position of sialic acid attachment since they produced the same glycoasparagine on incubation with the neuraminidase [EC 3.2.1.18] from Clostridium perfringens. The structure of the resulting sialic acid-free glycoasparagine was determined to be beta-Gal-beta-GlcNAc-beta-Gal-(1 leads to 4)-beta-GlcNAc-Asn based mainly on the results of sequential enzymatic degradations.
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PMID:Characterization of one neutral and two acidic glycoasparagines isolated from the urine of patients with aspartylglycosylaminuria (AGU). 18 76

1. The influence of internal and external Na concentrations on Ca movements have been measured in pinch-off presynaptic nerve terminals (synaptosomes). Ca uptake is enhanced when external Na (Nao) is replaced by Li, choline or dextrose, in Na-loaded synaptosomes. Depletion of internal Na (Nai) abolishes the stimulatory effect of external Na removal. 2. Ca uptake from Na-depleted media is proportional to [Na]i -2, and averages about 1-5 mumole Ca/g synaptosome protein per minute when [Na]i is approximately 137 mM. This may correspond to a Ca influx of about 0-1 p-mole/cm-2 sec. 3. External Na is a competitive inhibitor of the Nai-dependent Ca uptake. The interrelationship between [Na]o, [Ca]o and Ca uptake indicate that two external Na ions may compete with one Ca at each uptake site. 4. The distribution of particles with Nai-dependent Ca uptake activity parallels the distribution of synaptosomes in the preparative sucrose gradient. Thus, this Ca uptake activity is probably a property of the pinched-off nerve terminals per se, and not of the mitochondria which may contaminate the synaptosome fraction. 5. The Nai-dependent Ca uptake mechanism requires an intact surface membrane, since synaptosomes subjected to osmotic lysis lose the ability to accumulate Ca by this route. 6. Ca efflux into Ca-free media is largely dependent upon the presence of external Na. The curve relating Ca efflux to [Na]o is sigmoid, and suggests that more than one external Na ion (perhaps 2 or 3) is needed to activate the efflux of each Ca ion. 7. The net Ca gain exhibited by Na-loaded synaptosomes incubated in Na-depleted media can be accounted for by the increased Ca uptake and decreased Ca loss observed under these conditions. 8. Treatment of synaptosomes with cyanide or 2,4-dinitrophenol decreases Ca uptake and enhances Ca efflux into Na-containing media. This results in a net loss of Ca from the terminals, even in the presence of external Ca. 9. In contrast to the Ca efflux from synaptosomes, the Ca efflux from brain mitochondria is not dependent upon external Na, and is reduced by succinate, a substrate which is known to fuel mitochondrial respiration. 10. The temperature coefficient (Q10) of the Nai-dependent Ca uptake is about 3. 11. The Nai-dependent Ca uptake is reduced at low pH. The relationship between this Ca uptake and pH approximates a titration curve with a pKa of about 5-6. 12. The data indicate that Ca transport in rat brain presynaptic terminals may involve a carrier-mediated Na-Ca exchange mechanism, and that some of the energy required for Ca extrusion may come from the Na electrochemical gradient across the surface membranes.
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PMID:The influence of sodium on calcium fluxes in pinched-off nerve terminals in vitro. 23 34

A glucose-binding glycoprotein (GBP) from the periplasm of Pseudomonas aeruginosa was purified to homogeneity as judged by polyacrylamide gel electrophoresis, molecular sieve chromatography, and double-diffusion gel precipitation. It had an average molecular weight of 44,500 and an isoelectric point of 4.7. One mole of glucose was bound per mole of GBP with a dissociation constant of 0.35 muM. The binding of radioactive glucose by GBP was not significantly inhibited by 10-fold-higher concentrations of other carbohydrates; however, a number of related compounds were found to compete at 100-fold-higher concentrations. Amino acid analyses revealed predominant amounts of alanine, glutamate, and glycine and a low content of sulfur-containing amino acids. The carbohydrate moiety of GBP, comprising nearly 16% of the total weight, contained galactosamine, glucosamine, fucose, galactose, glucose, and mannose. A GBP-deficient mutant, strain MB723, was found to be defective in both membrane transport and glucose chemotaxis. Strain MB724, a revertant to GBP-positive phenotype, simultaneously recovered normal levels of both membrane functions.
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PMID:Purification and properties of the periplasmic glucose-binding protein of Pseudomonas aeruginosa. 40 16

Solutions of ampicillin, carbenicillin, methicillin, oxacillin, penicillin G, and cephalothin in 5% dextrose were analyzed by nickel(II)-catalyzed hydroxylaminolysis. The reactions of these antibiotics were complete within 20 min at room temperature. Under the analytical conditions, molar absorptivities of the ferric-hydroxamate complexes ranged from 830 to 1005 liters/mole/cm. Coefficients of variation for the analysis of these antibiotics in 5% dextrose were typically less than 3% at concentrations of 1 mg/ml. Oxacillin was analyzed by the same method in normal saline and/or lactated Ringer solutions. The method also was applied to the analysis of chloramphenicol in aqueous solutions. Only ampicillin showed a significant decrease in concentration in 48 hr.
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PMID:Colorimetric determination of penicillins and related compounds in intravenous solutions by nickel (II)-catalyzed hydroxamic acid formation. 51 76


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