UMLS:C0027960 - FACTA Search

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)

Manganese and copper were released from spinach chloroplasts by NaCN-treatment, though iron was not affected. The Hill reaction activity was also inhibited by this treatment, but was partially recovered by the addition of either Mn2+ or Cu2+, but not of Fe3+. The interaction of Mn2+ with manganese-depleted chloroplasts by NaCN-treatment was studied using 54Mn2+. A Scatchard plot shows the high and low affinity binding sites of Mn2+ on NaCN-treated chloroplast membrane; high affinity binding being specific for NaCN-treated chloroplast with a binding constant, KH, of 1.9 X 10(5) M-1, and a maximum binding number, NH, of 0.0016 g-atom per mole of chlorophyll. The low binding site was also found on untreated chloroplasts; its binding constant, KL, being 1.2 X 10(4) M-1, and its maximum binding number, NL, of 0.0112 g-atom per mole oc chlorophyll at pH 8.2 NH was proportional to the degree of the removal of Mn by NaCN-treatment and was constant at pH 4--9. NL markedly increased at a high pH with a midpoint of pH 7.9 indicating the exposure of a new, similar binding site. Light illumination partially inhibited the binding of Mn2+. Within 1 min in the dark the binding reaction reached equilibrium in the absence of pyrophosphate, however, 20 min were required to transform into pyrophosphate-resistant form. The pH dependence of the binding of Mn2+ with pKa 7.2 and the ineffectiveness of p-chloromercuribenzoate suggest the possible ligand of Mn2+ is the imidazole nitrogen of the histidine residue.
...
PMID:Removal of Mn from spinach chloroplasts by sodium cyanide and the binding of Mn2+ to Mn-depleted chloroplasts. 0 74

Superoxide dismutase has been isolated and characterised from the extreme thermophile Thermus aquaticus. The pure enzyme is a reddish-purple manganese-containing protein with a molecular weight of approximately 80000 +/- 5000. Combination of gel electrophoresis in dodecylsulphate and amino acid analysis shows that it is composed of four identical subunit polypeptide chains consisting of approximately 186 amino acids. The tetrameric protein contains two atoms of manganese. A stable manganese-free apoprotein has been prepared by treatment with EDTA in 8 M urea at acidic pH. The apoprotein regains the tetrameric structure in the absence of manganese but is inactive. Reconstitution of active Mn-enzyme was achieved byaddition of Mm2+ apoprotein in 8 M urea at acid pH. Reconstitution was monitored by absorption spectroscopy, manganese analysis and regain of activity and by these criteria the reconstituted enyzme with two atoms Mn per mole is indistinguishable from the native enzyme. The enhanced stability of the thermophile apoenzyme and Mn-enzyme is of advantage for studies of the structure and mechanism of action of superoxide dismutase. The N-terminal amino acid sequence to the 40th residue of the submit was determined by automated Edman degradation. The sequence has a close resemblance to that of the dimeric Mn-enzyme from another thermophile, Bacillus stearothermophilus.
...
PMID:Superoxide dismutase from Thermus aquaticus. Isolation and characterisation of manganese and apo enzymes. 1 28

The guanylate cyclase activity of axoneme--basal apparatus complexes isolated from bovine retinal rods has been investigated. The Mg2+ and Mn2+ complexes of GTP4- serve as substrates. Binding of an additional mole of Mg2+ or Mn2+ per mole of enzyme is required. Among cations which are ineffective are Ca2+, Ni2+, Fe2+, Fe3+, Zn2+, and Co2+. The kinetics are consistent with a mechanism in which binding of Mg2+ or Mn2+ to the enzyme must precede binding of MgGTP or MnGTP. The apparent dissociation constants of the Mg--enzyme complex and the Mn--enzyme complex are 9.5 x 10(-4) and 1.1 x 10(-4) M, respectively. The apparent dissociation constants for binding of MgGTP and MnGTP to the complex of the enzyme with the same metal are 7.9 x 10(-4) and 1.4 x 10(-4) M, respectively. The cyclase activity is maximal and independent of pH between pH 7 and 9. KCl and NaCl are stimulatory, especially at suboptimal concentrations of Mg2+ or Mn2+. Ca2+ and high concentrations of Mg2+ and Mn2+ are inhibitory. Ca2+ inhibition appears to require the binding of 2 mol of Ca2+ per mol of enzyme. The dissociation constant of the Ca2--enzyme complex is estimated to be 1.4 x 10(-6) M2. The axoneme--basal apparatus preparations contain adenylate cyclase activity whose magnitude is 1--10% that of the guanylate cyclase activity.
...
PMID:Guanylate cyclase of isolated bovine retinal rod axonemes. 4 May 95

1. While below 10 degrees C, the initial burst of Pi liberation in the hydrolysis of Mn(II)-ATP by heavy meromyosin or myosin subfragment 1 was inhibited by the pre-addition of ADP without any change in the steady-state activity, it was not inhibited above 10 degrees C. The burst size was about one mole per two moles of myosin active sites. 2. Above 10 degrees C, the ultraviolet absorption spectrum of heavy meromyosin induced by ATP in MnCl2 was similar to that induced in MgCl2 and the spectral decay to the ADP-induced level occurred only after all the ATP in the solution was depleted. In contrast, below 10 degrees C the spectrum induced by ATP in MnCl2 decayed to the ADP-induced level within a few seconds after the addition of ATP, although ATP was present in the solution. 3. These two results indicate that in Mn-ATP above 10 degrees C at the burst site there is a myosin*-ADP-Pi complex generated by ATP hydrolysis while below 10 degrees C there is a myosin-product complex identical with the one generated by adding ADP (and Pi) to myosin. 4. At tempertures both above and below 10 degrees C, the Mn-ATP hydrolysis of heavy meromyosin was activated by actin and superprecipitation of actomyosin occurred. Characteristics of these phenomena showed a transition at around 10 degrees C.
...
PMID:Temperature-dependent transitions of the myosin-product intermediate at 10 degrees C in the Mn(II)-ATP hydrolysis. 12 63

The initial burst of Pi liberation during the hydrolysis of Mn(II)-ATP by heavy meromyosin from rabbit psoas muscle was investigated. Below 10 degrees, the initial burst of Pi liberation was inhibited by the pre-addition of ADP without any change in the steady-state activity, but it was not inhibited above 10 degrees. The burst size was about one mole per mole of heavy meromyosin. The initial burst of Pi liberation in Mg-ATP hydrolysis at 8 degrees, however, was not inhibited by the pre-addition of ADP. These results, obtained with psoas muscle heavy meromyosin, were almost the same as those obtained with heavy meromyosin from rabbit leg and back muscles (Hozumi and Tawada (1975) Biochim. Biophys. Acta 376, 1-12) and, therefore, indicate that in Mn-ATP above 10 degrees there is at the burst site a predominant myosin -product complex generated by ATP hydrolysis. Similarly, below 10 degrees there is a myosin-product complex identical with the one generated by adding ADP (and Pi) to myosin.
...
PMID:Temperature-dependent transitions of the myosin-product intermediate at 10 degrees during Mn(II)-ATP hydrolysis by myosin from rabbit psoas muscle. 13 32

Rat and calf adrenal cortex homogenates were found to contain three different malic enzymes. Two were strictly NADP+-dependent and were localized, one each, in the cytosol and the mitochondrial fractions, respectively. These two enzymes appear to be identical to those described by Simpson and Estabrook (Simpson, E. R., and Estabrook, R. W. (1969) Arch. Biochem. Biophys. 129, 384-395). The third was NAD(P)+-linked and was present in the mitochondrial fraction only. All three malic enzymes separated as distinct bands during electrophoresis on 5 percent polyacrylamide slab gels at pH 9.0. Marker enzymes and the mitochondrial malic enzymes migrated together in intact mitochondria during sucrose density gradient centrifugations despite changes in the equilibrium position of the mitochondria promoted by energy-dependent calcium phosphate accumulation. In adrenal cortex mitochondria subfractionated by the method of Sottocasa et al. (SOTTOCASA, G.L., KUYLENSTIERNA, B., ERNSTER, L., and BERGSTAND, A. (1967) J. Cell Biol. 32, 415-438), both malic enzymes were associated with the inner membrane-matrix space. Sonication solubilized the two malic enzymes along with the matrix space marker enzymes. The NAD(P)+-dependent malic enzyme was purified 100-fold from calf adrenal cortex mitochondria. The final preparation was free of malic dehydrogenase, fumarase, the strictly NADP+-linked malic enzyme and adenylate kinase. Either Mn24 orMg2+ was required for activity and 1 mol of pyruvate was formed for each mole of NAD+ and NADP+ reduced. The pH optima with NAD+ and NADP+ were 6.5 tp 7.0 and 6.0 to 6.5, respectively. Michaelis-Menten kinetics were observed on the alkaline side. Fumarate, succinate, and isocitrate were positive and ATP and ADP were negative modulators of the regulatory enzyme. The modulators did not influence the stoichiometry and they were not metabolized during the reaction. Under Vmax conditions the ratios for the rate of NAD+:NADP+ reduction were 1.76 and 1.15 at pH 7.4 and 6.0, respectively. The apparent Michaelis constants also differed depending on the pH and the coenzyme. At pH 7.4 (in the presence of 5 mM fumarate) and at pH 6.0 (no fumarate) the Km values for (-)-malate, NAD+, and Mn2+ were 1.7, 0.16, and 0.15 mM, and 0.31, 0.06, and 0.09 mM, respectively. At pH 7.4 (5MM fumarate) and pH 6.0 (no fumarate), the Km values for (-)-malate, NADP+, and Mn2+ were 6.5, 0.62, and 0.59 mM, and 0.68. 0.12, and 0.31 mM, respectively. The apparent Ki values for ATP with NAD+ and NADP+ as coenzyme were 0.42 and 0.27 mM, respectively.
...
PMID:The mitochondrial malic enzymes. I. Submitochondrial localization and purification and properties of the NAD(P)+-dependent enzyme from adrenal cortex. 23 89

1. Membrane potential changes produced by adenosine and adenine nucleotides, acetylcholine, and vagus nerve stimulation were studied by intracellular recording in the sinus venosus of the frog, Rana pipiens. 2. Acetylcholine (ACh) released from the vagus nerve terminals evoked a slow hyperpolarization lasting several seconds in the cells of the sinus. Ionophoretic application of ACh from a micropipette produced a response which is similar in time course and amplitude to that evoked by vagus nerve stimulation. Bath application of ACh caused a steady hyperpolarization in quiescent preparations, or cessation of action potential generation in spontaneously active preparations. 3. Adenosine and adenine nucleotides produced hyperpolarizations when applied by addition to the bath or by ionophoresis from micropipettes. The hyperpolarization produced by ionophoresis of adenine compounds was somewhat slower than that produced by ACh. 4. Adenosine and the adenine nucleotides, 5'-AMP, 3'-AMP, 2'-AMP, and 5'-atp were virtually equipotent in their action. Adenosine was at least 1000-fold more potent than other purine and pyrimidine nucleosides or adenine. Both the ribose and adenine groups were important for agonist activity. 5. The concentrations of agonist required to produce half-maximal responses were estimated from dose--response curves as 3 x 10(-7) M for ACh and 2 x 10(-6) M for ATP. ACh is about 7 times more potent than ATP in producing a hyperpolarization. 6. Adenine compounds act directly upon the cardiac muscle fibres: bath or ionophoretically applied adenine compounds act even when transmitter release from nerve terminals is blocked with high (Mn2+) or when ACh receptors are blocked with atropine. 7. Adenine compounds act on the surface of the muscle fibre membrane. Analogues of adenosine which do not enter the cell are potent agonists of the receptor. An adenyl oligonucleotide too large to enter the cell was 2.6 times more potent per mole than adenosine in producing a hyperpolarization. Drugs such as dipyridamole and 6-(2-hydroxy 5-nitrobenzyl) thioguanosine, which are potent blockers of adenosine transport, potentiate the response of the sinus cells to adenosine. 8. Aminophylline and theophylline are competitive antagonists of adenosine action. The apparent Ki for aminophylline inhibition was 5 microM. 9. The response produced by adenine compounds is partly caused by an increase in the permeability of the membrane to K+. The maximum response to both ACh and adenine nucleotides approached the estimated level of EK or ECl. Replacing extracellular chloride with impermeant isethionate had no effect on responses to ACh or adenine nucleotides. The hyperpolarization was not produced by an activation of an ouabain-sensitive pump since 20 microM-ouabain had little effect on the response to adenosine. 10. The response to vagus nerve stimulation is completely blocked by 50 nM-atropine...
...
PMID:Adenosine receptors in frog sinus venosus: slow inhibitory potentials produced by adenine compounds and acetylcholine. 31 61

Manganese-containing superoxide dismutase was isolated from an extreme thermophile, Thermus thermophilus HB8. About 150 mg of the enzyme was obtained from 500 g of wet cells. The enzyme was easily crystallized in octahedra from ammonium sulfate solution. The molecular weight of the enzyme was determined to be 8.2 X 10(4) and 8.4 X 10(4) by sedimentation equilibrium and gel-filtration, respectively. The enzyme contains 2 atoms of manganese per mole and consists of four subunits of identical molecular weight, about 2.1 X 10(4). The amino acid composition of the enzyme is similar to that of the superoxide dismutase of Thermus aquaticus. Proline was detected as the N-terminal amino acid. The isoelectric point was determined to be pH 6.0 by the electrofocusing method. The enzyme has maxima at 283 nm and 480 nm in the absorption spectrum. The CD spectrum suggests that the enzyme has a high alpha-helical content.
...
PMID:Purification and properties of superoxide dismutase from Thermus thermophilus HB8. 65 88

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

1. A superoxide dismutase [EC 1.15.1.1] was purified about 275-fold with a yield of 34% from Mycobacterium tuberculosis, strain H37Ra (attenuated strain), grown on a Sauton medium for two months. The purified enzyme was homogeneous as judged by polyacrylamide gel electrophoresis, and by analytical ultracentrifugation and sedimentation equilibrium studies. 2. The molecular weight of the enzyme was estimated to be approximately 88,000 by sedimentation equilibrium analysis. Since the molecular weight of the subunit was 21,000 as determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis, the enzyme appears to be composed of four subunits of equal size. 3. Electron spin resonance (ESR) spectra showed that the enzyme contained ferric iron, and metal analysis showed that the enzyme contained ferric iron, and metal analysis showed that approximately 3.7 atoms of iron were present per mole of the enzyme, indicating the occurrence of 1 atom of iron per subunit. 4. The amino acid composition was apparently similar to those of the iron-containing superoxide dismutases from Escherichia coli, luminous bacteria, Pseudomonas ovalis, and blue-green alga. 5. Antibodies against the enzyme were raised in rabbits and immunological studies were performed. The enzyme from M. tuberculosis, strain H37Rv (virulent strain), was found to have antigenic structures identical with those of the H37Ra enzyme. On the other hand, the manganese-containing superoxide dismutases from other species of mycobacteria, i.e., Mycobacterium species, strain Takeo, M. phlei and M. lepraemurium, showed only partial immunological identity with the H37Ra enzyme. 6. During the growth of M. tuberculosis, strain H37Ra, the enzyme was found to be secreted into the culture medium.
...
PMID:Superoxide dismutase from Mycobacterium tuberculosis. 82 61

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