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

The defect in urinary acidification induced by amphotericin B (AMB) was further characterized in turtle bladder. Since AMB has been shown to increase the hydrogen ion (H+) permeability of this epithelium in the absence of exogenous bicarbonate ions (HCO3-), we explored the permeability characteristics in the presence of imposed bicarbonate ion gradients, comparable to those occurring in vivo. With mucosal (M) pH lowered to the point of zero net hydrogen ion secretion, the transepithelial flow of bicarbonate ions (JHCO3) from serosa (S) to M was 0.91 +/- .06 y mole/hr in response to a 20 mM HCO3- gradient. After AMB addition to M, back diffusion of hydrogen ions from M to S (-JH) increased from zero to 0.36+/-0.05 micronmole/hr, whereas bicarbonate ion transport from S to M (JHCO3) failed to increase (0.91+/-0.06 before and 0.82+/-0.09 micronmole/hr after AMB). In contrast to M addition, S addition of AMB had no effect on either -JH or JHCO3. The defect in urinary acidification induced by AMB is characterized by a large increase in the permeability for hydrogen ions rather than that for bicarbonate ions and depends on direct exposure of the luminal cell membrane to AMB. The permeability increase is cation selective, not only for hydrogen ions but also, as shown previously, for potassium ions, and to a lesser extent, for sodium ions. The results are consistent with the formation by AMB of aqueous half pores in the luminal membrane. Although the passive permeabilities for bicarbonate and chloride ions are not affected primarily, they may increase after prolonged exposure, probably as a results of paracellular leaks that are not specific for AMB.
 ...
PMID:Acidifying defect induced by amphotericin B: comparison of bicarbonate and hydrogen ion permeabilities. 1 60

Ribulose-diphosphate carboxylase from Thiobacillus novellus has been purified to hemogeneity as observed by polyacrylamide gel electrophoresis and U.V. light observation during sedimentation velocity analysis. The optimum pH for the enzyme with Tris-HCl buffers was about 8.2. Concentrations of this buffer in excess of 80 mM were inhibitory. The apparent Km for RuDP was about 14.8 muM with a Hill value of 1.5, for HCO3- the apparent Km was about 11.7 mM with an n value of 1.18 and for Mg2+ about 0.61 mM. The enzyme was specific for this cation. Relatively high concentrations of either Hg2+ or pCMB were required before significant inhibition was observed. Activity declined slowly during a 4-hr incubation period in either 3.0 M or 8.0 M urea. Incubation for 12 hrs resulted in complete loss of activity which was not prevented by 10 mM Mg2+ and was not reversed by dialysis and subsequent addition of 10 mM cysteine. Polyacrylamide gel electrophoresis revealed a loss of the major band and the appearance of 2 new bands. SDS polyacrylamide gel electrophoresis gave an average M.W. of 73500 +/- 2500 for the slower moving band and 12250 +/- 2500 for the faster moving. However, incubation in urea for up to 40 hrs revealed a decrease in the M.W. of the slower moving band to about 60000. The Ea for the enzyme was calculated to be about 18.85 kcal mole-1, with the possibility of a "break" between 40 and 50 degrees C. The Q10 was 3.07 between 20 and 30 degrees C whereas between 30 to 40 degrees C it was 3.31. Only phosphorylated compounds caused significant inhibition of enzyme activity. They included ADP, FDP, F6P, G6P, PEP, 6PG, 2-PGA, R1P, R5P, and Ru5p.
 ...
PMID:Properties and regulation of ribulose diphosphate carboxylase from Thiobacillus novellus. 24 94

1. Bicarbonate transport across human red cell membranes was studied between 0 and 10 degrees C at alkaline pH values by determining the efflux of 14C-labelled bicarbonate from resealed erythrocyte ghosts. Transfer of labelled CO2 was eliminated as a source of error, when formation of intracellular 14CO2 was inhibited with carbonic anhydrase inhibitors. The study showed that there are no fundamental differences between the characteristics of bicarbonate and of chloride self-exchange as has been inferred from previous studies of chloride-bicarbonate exchange. 2. Efflux of radioactivity could be reduced more than 99% by reversible and irreversible inhibitors of anion transport. Inhibition of both chloride and bicarbonate self-exchange was linearly related to the binding of 4,4'-diisothiocyanostilbene-2,2'-disulphonic acid (DIDS) to the membranes. Complete (i.e. greater than 99%) inhibition was obtained after binding of 1.2 x 10(6) DIDS molecules per cell. 3. Bicarbonate self-exchange proved a saturable function of bicarbonate concentration, with a maximum at external and internal concentrations of approximately 100 mM, showing self-depression at higher bicarbonate concentrations, and half-maximum exchange flux at a concentration of 10 mM. The results were consistent with the hypothesis that the exchange mechanism has two anion binding sites, one mediating ion transport and the other causing transport inhibition. 4. Maximum exchange flux of bicarbonate was about 30% larger thant that of chloride, and the affinity of bicarbonate for the transport site was about three times larger than that of chloride. The apparent activation energy of bicarbonate exchange was 28 kcal/mole, the same order of magnitude as found for other inorganic anions between 0 and 10 degrees C. 5. The ability of other inorganic anions to exchange with bicarbonate decreased in the sequence Cl greater than NO3 greater than F greater than Br greater than or equal to I, corresponding to the sequence of the rate of self-exchange of halides. 6. Counter-transport of bicarbonate could be driven by a chloride gradient, when ghosts containing KCl were suspended in a medium containing traces of labelled bicarbonate in addition to a non-permeating anion. Concentration ratios (ci/co) up to about 1000 could be obtained. 7. It is concluded that bicarbonate is transported by the inorganic anion exchange mechanism of the erythrocyte membrane. The slight differences between the exchange kinetics of chloride and bicarbonate were explained by differing affinities of the two anions for the two anion binding sites of the transport system.
 ...
PMID:Bicarbonate exchange through the human red cell membrane determined with [14C] bicarbonate. 51 56

Bicarbonate appearance in the lumen and its relationship to solute absorption were studied in a Pavlov pouch in the cardiac region of the first compartment of the llama forestomach. HCO3- appearance showed no diurnal variation. HCO3- accumulation was highly dependent on the pH of the solution used. The HCO3- ion probably is formed from CO2 diffusing into the lumen from the serosal side, as a result of cell metabolism and of OH- ions. HCO3- accumulation was closely related to volatile fatty acid (VFA) absorption. The ratio of HCO3- appearance to VFA absorption depended on the pH of the solution. At a pH of 6.6, about 0.1 mol HCO3- and, at a pH of 7.8, 0.9 mol HCO3- appeared per mole absorbed VFA, indicating that at slightly alkaline pH nearly all H+ ions required for the nonionic absorption of VFA appeared to be delivered from the dissociation of H2CO3. Bicarbonate gain and VFA absorption were increased when animals were not fed for 48 h. Sodium absorption was related to VFA as well as water absorption.
 ...
PMID:Bicarbonate secretion and solute absorption in forestomach of the llama. 67 5

D-Ribulose-1,5-bisphosphate (RuBP) carboxylase has been purified from glutamate-CO2-S2O3(2)-grown Thiobacillus intermedius by pelleting the enzyme from the high-speed supernatant and by intermediary crystallization followed by sedimentation into a discontinuous 0.2 to 0.8 M sucrose gradient. The enzyme was homogeneous by the criteria of electrophoresis on polyacrylamide gels of several acrylamide concentrations, sedimentation velocity and equilibrium measurements, and electron microscopic observations of negatively stained preparations. The molecular weights of the enzyme determined by sedimentation equilibrium and light-scattering measurements averaged 462,500 +/- 13,000. The enzyme consisted of closely similar or identical polypeptide chains of a molecular weight of 54,500 +/- 5,450 determined by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The S(0)20,w of the enzyme was 18.07S +/- 0.22. Electron microscopic examination suggested that the octomeric enzyme (inferred from the molecular measurements mentioned) had a cubical structure. The specific activity of the enzyme was 2.76 mumol of RuBP-dependent CO2 fixed/min per mg of protein (at pH 8 and 30 C), and the turnover number in terms of moles of CO2 fixed per mole of catalytic site per second was 2.6. The enzyme was stable for 3 months at -20 C and at least 4 weeks at 0 C. The apparent Km for CO2 was 0.75 mM, and Km values for RuBP and Mg2+ were 0.076 and 3.6 mM, respectively. Dialyzed enzyme could be fully reactivated by the addition of 20 mM Mg2+ and partially reactivated by 20 mM Co2+, but Cd2+, Mn2+, Ca2+, and Zn2+ had no effect. The compound 6-phosphogluconate was a linear competitive inhibitor with respect to RuBP when it had been preincubated with enzyme, Mg2+, and HCO3-.
 ...
PMID:Purification, quaternary structure, composition, and properties of D-ribulose-1,5-bisphosphate carboxylase from Thiobacillus intermedius. 81 23

The carbon dioxide solubility coefficient, alphaCO2, and the apparent carbonic acid dissociation constants, K'1 and K'2 were estimated in the serum of the crab Carcinus maenas at various temperatures and ionic strengths. At 15 degrees C, the indirectly determined alphaCO2 value is 0-0499 m-mole l-1 torr-1 for crabs living in normal sea water (salinity ca. 35 percent). It is apparently independent of the serum protein concentration and of the stage of the moulting cycle. For crabs living in undiluted sea water, the mean pK'1 value, determined either gasometrically or titrimetrically, is 6-027 at 15 degrees C. At the same temperature, pK'2=9-29. These values approximate to those of sea water at 35 percent salinity. pK'1 drops as temperature rises; the measured deltapK'1/deltat is -0-0053 pH unit degrees C-1 between 10 and 30 degrees C. PK'1 rises as the ionic strength is lowered. Alignment nomograms have been constructed for the determination of alphaCO2, pK'1 and pK'2 values in relation to various conditions of temperature and salinity.
 ...
PMID:Carbon dioxide combining properties of the blood of the shore crab Carcinus maenas (L): carbon dioxide solubility coefficient and carbonic acid dissociation constants. 127 Sep 94

The following methods are described for the analytical investigation of pipecuronium bromide. 1. HPLC method. Of the several systems tried for the separation and quantification of impurities and degradation products the best results were obtained using silica as the stationary phase and 43:43:14 mixture of methanol, acetonitrile and concentrated aqueous ammonia containing 0.1 mole/l each of ammonium chloride and ammonium carbonate as the eluent. The validation of this method is presented. The above described aggressive eluent can be successfully replaced by an ion-pairing system using silica as the stationary phase and 96:4 mixture of acetonitrile and water containing 0.1 mole/l sodium perchlorate as the eluent. 2. Thin-layer chromatography. TLC systems are described for the separation and densitometric quantification of the impurities and degradation products of pipecuronium bromide. 3. Spectrophotometry. Two methods are described. The ester groups of the molecule can be determined by the iron(III)-hydroxamate method while for the ion-pair extraction of the quaternary ammonium steroid picric acid or bromthymol blue are used as the reagents. 4. Titrimetry. In addition to the titration with acetous perchloric acid for the assay of the bulk material a microtitration method is described for the determination of pipecuronium bromide in individual lyophylized ampoules (potentiometric titration with 0.1 M silver nitrate).
 ...
PMID:[Analysis of steroids. Part 45: Analytical investigation of pipecuronium bromide (Arduan)]. 132 18

Single channel currents though apical membrane Cl channels of the secretory epithelial cell line T84 were measured to determine the anionic selectivity and concentration dependence of permeation. The current-voltage relation was rectified with single channel conductance increasing at positive potentials. At 0 mV the single channel conductance was 41 +/- 2 pS. Permeability, determined from reversal potentials, was optimal for anions with diameters between 0.4 and 0.5 nm. Anions of larger diameter had low permeability, consistent with a minimum pore diameter of 0.55 nm. Permeability for anions of similar size was largest for those ions with a more symmetrical charge distribution. Both HCO3 and H2PO4 had lower permeability than the similar-sized symmetrical anions, NO3 and ClO4. The permeability sequence was SCN greater than I approximately NO3 approximately ClO4 greater than Br greater than Cl greater than PF6 greater than HCO3 approximately F much greater than H2PO4. Highly permeant anions had lower relative single channel conductance, consistent with longer times of residence in the channel for these ions. The conductance sequence for anion efflux was NO3 greater than SCN approximately ClO4 greater than Cl approximately I approximately Br greater than PF6 greater than F approximately HCO3 much greater than H2PO4. At high internal concentrations, anions with low permeability and conductance reduced Cl influx consistent with block of the pore. The dependence of current on Cl concentration indicated that Cl can also occupy the channel long enough to limit current flow. Interaction of Cl and SCN within the conduction pathway is supported by the presence of a minimum in the conductance vs. mole fraction relation. These results indicate that this 40-pS Cl channel behaves as a multi-ion pathway in which other permeant anions could alter Cl flow across the apical membrane.
 ...
PMID:Anion permeation in an apical membrane chloride channel of a secretory epithelial cell. 137 74

Phosphoenolpyruvate carboxylase (EC4.1.1.31), which catalyzes the carboxylation of phosphoenolpyruvate to produce oxaloacetate was purified 465-fold from extracts of organotrophically grown Thiobacillus novellus. Nondenaturing polyacrylamide gel electrophoresis (PAGE) of the purified enzyme revealed the presence of two bands after staining with Buffalo Black. Gels stained with Fast Violet B after incubation with PEP, HCO3-, Mg2+ and acetyl CoA also showed two bands of activity with the faster moving the more active of the two. Sodium dodecylsulfate (SDS)-PAGE of the enzyme heated at 100 degrees C for 5 min revealed the presence of three intensely stained bands of M(r) 95 K, 51 K, and 28 K. However, electrophoresis of the enzyme heated for 2 min showed a single band of about 100 K, indicating that the preparation was likely homogeneous. The 51 K and 28 K subunits are thus products of the 95 K subunit. Gel filtration studies of the native enzyme yielded a M(r) of 360 K. Therefore, the enzyme is a tetramer. The optimum pH in Tris buffer was 8.0, with Km for PEP 0.64 mM, HCO3- 0.11 mM, and acetyl CoA a potent activator, 1.3 microM. A divalent cation best served by Mg2+ gave sigmoidal initial velocity plots. Hill plots of the data gave coefficients (nH) of 2.6. None of the metabolites tested, nucleotide triophosphates excepted, significantly affected enzyme activity. Binding studies with 14C-labelled PEP revealed the binding of about 20 moles PEP per mole (360,000 g) of PEPC. Initial velocity studies suggest that the reaction is catalyzed by a random Bi Bi mechanism. Despite the lack of inhibition by certain metabolites, the enzyme's function is probably anaplerotic.
 ...
PMID:Purification and characterization of the phosphoenolpyruvate carboxylase from the facultative chemolithotroph Thiobacillus novellus (ATCC 8093). 141 12

In bicarbonate/CO2 buffer, Mn(II) and Fe(II) catalyze the oxidation of amino acids by H2O2 and the dismutation of H2O2. As the Mn(II)/Fe(II) ratio is increased, the yield of carbonyl compounds per mole of leucine oxidized is essentially constant, but the ratio of alpha-ketoisocaproate to isovaleraldehyde formed increases, and the fraction of H2O2 converted to O2 increases. In the absence of Fe(II), the rate of Mn(II)-catalyzed leucine oxidation is directly proportional to the H2O2, Mn(II), and amino acid concentrations and is proportional to the square of the HCO3- concentration. The rate of Mn(II)-catalyzed O2 production in the presence of 50 mM alanine or leucine is about 4-fold the rate observed in the absence of amino acids and accounts for about half of the H2O2 consumed; the other half of the H2O2 is consumed in the oxidation of the amino acids. In contrast, O2 production is increased nearly 18-fold by the presence of alpha-methylalanine and accounts for about 90% of the H2O2 consumed. The data are consistent with the view that H2O2 decomposition is an inner sphere (cage-like) process catalyzed by a Mn coordination complex of the composition Mn(II), amino acid, (HCO3-)2. Oxidation of the amino acid in this complex most likely proceeds by a free radical mechanism involving hydrogen abstraction from the alpha-carbon as a critical step. The results demonstrate that at physiological concentrations of HCO3- and CO2, Mn(II) is able to facilitate Fenton-type reactions.
 ...
PMID:Manganese(II) catalyzes the bicarbonate-dependent oxidation of amino acids by hydrogen peroxide and the amino acid-facilitated dismutation of hydrogen peroxide. 229 94


1 2 3 4 5 6 7 8 9 10 Next >>