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Query: UMLS:C0009443 (cold)
 92,137 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effects of palmitic acid on skeletal muscle mitochondria isolated from the hind limb muscle of cold and warm acclimated rats were studied. At higher concentrations of the fatty acid, a greater depression of both ADP/O and RCR (respiratory control ratio) was observed in the cold acclimated group. Initial ADP/O and RCC however, were higher in the cold acclimated group. The enhanced sensitivity of skeletal muscle mitochondria of the cold acclimated rat is discussed.
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PMID:The effects of palmitic acid on skeletal muscle mitochondria of cold and warm acclimated rats. 7 Oct 86

1. The bound nucleotides of the beef-heart mitochondrial ATPase (F1) are lost during cold inactivation followed by (NH4)2SO4 precipitation. The release of tightly bound ATP parallels the loss of ATPase activity during this process. 2. During cold inactivation, the sedimentation coefficient (s20, w) of the ATPase first declines from 12.1 S to 9 S, then to 3.5 S. (NH4)2SO4 precipitation of the 9-S component also leads to dissociation into subunits with s20, w of 3.5 S. 3. The 9-S component still contains the bound nucleotides, which are removed when it dissociated into smaller subunits. 4. Reactivation of cold-inactivated ATPase by incubation at 30 degrees C is increased by the presence of 25% glycerol. ATP, however, does not have any clearcut effect on the degree of reactivation in the presence of glycerol. 5. ADP is an inhibitor of the reactivation, probably because it exchanges during reactivation for bound ATP giving rise to an inactive 12-S component. 6. The exchange of tightly bound nucleotides with added adenine nucleotides is more extensive and faster with cold-inactivated ATPase than with the native enzyme. During reactivation up to 1.6 moles of ATP and 1.0 mole ADP can exchange per mole enzyme. 7. Incubation with GTP, CTP or inorganic pyrophosphate induces an increased activity of the ATPase, which, however, soon declines in the presence of ATP. It also disappears on precipitation of GTP-treated enzyme with (NH4)2SO4.
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PMID:Nucleotide-binding properties of native and cold-treated mitochondrial ATPase. 12 64

Membrane-bound ATPase (EC 3.6.1.3) of Escherichia coli K 12 is released in a soluble form by the mechanical treatments applied to the cells in order to break them. The purification of the soluble enzyme is described. The purified protein gives a single band in 7.5% polyacrylamide gel electrophoresis. The molecular weight is estimated to be 350 000. The enzyme is cold-labile, Mg-2+ dependent, insensitive to inhibition by N, N'-dicyclohexylcarbodiimide and specific for ATP and ADP. Membranes depleted of their ATPase activity by dilution in a buffer of low ionic strength and without Mg-2+ are able to incorporate the purified ATPase only in the presence of 2-6 mM Mg-2+. ATPase binds to particles formed by complementation between supernatant extracts of chl A and chl B mutants. There are three kinds of particles of different buoyant densities (1.10, 1.18 and 1.23); ATPase binds only to the 1.10 and 1.18 particles. The kinetics of incorporation have been studied. ATPase begins to be incorporated into the 1.10 particles after 10 min of incubation up to a maximum at 20 min: from 30 min, ATPase is incorporated only into 1.18 particles and the amount of incorporated ATPase increased in proportion with the peak of 1.18 particles. These kinetics have a hyperbolic pattern. In order to explain the mechanism of assembly involved in complementation, two hypotheses are proposed.
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PMID:Membrane reconstitution in chl-r mutants of Escherichia coli K 12. VII. Purification of the soluble ATPase of supernatant extracts and kinetics of incorporation into reconstituted particles. 12 90

The membrane-bound coupling factor from Mycobacterium phlei was solubilized from membrane vesicles by washing with low ionic strength buffer or 0.25 M sucrose. The solubilized enzyme exhibited coupling factor, latent ATPase, and succinate oxidation-stimulating activity. Purification by affinity chromatography using Sepharose coupled to ADP yielded a homogeneous preparation of latent ATPase which was purified about 200-fold with an 84% yield in a single step. Purified latent ATPase exhibited coupling factor activity but no succinate oxidation-stimulating activity. The molecular weight of latent ATPase was determined to be 250,000 +/- 10,000 by Sephadex G-200 chromatography. The ATPase was unmasked by trypsin treatment and activated by Mg2+ ion. However, trypsin treatment inactivated the coupling factor activity in the purified enzyme, indicating that the catalytic sites for ATPase and coupling activity are different. Unlike mitochondrial ATPase, latent ATPase from M. phlei was not cold-labile. Of the nucleoside triphosphates, UTP, ITP, and epsilon-ATP (1-N6-ethenoadenosine triphosphate) were hydrolyzed to a lesser extent compared to ATP. Kinetic data showed that ADP acted as a competitive inhibitor of latent ATPase activity with a Ki of 5 x 10(-3) M. Uncouplers of oxidative phosphorylation and respiratory inhibitors did not affect the latent ATPase activity, while sodium azide (0.1 mM) inhibited the latent ATPase activity.
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PMID:Energy-transducing membrane-bound coupling factor-ATPase from Mycobacterium phlei. I. Purification, homogeneity, and properties. 12 54

1. Oligomycin-insensitive ATPase (ATP phosphohydrolase, EC 3.6.1.3) was purified from brown adipose tissue mitochondria. It had a specific activity of 50 units/mg which could be increased up to 85 units/mg by KHCO3. The isolated enzyme represented less than 0.5% of the initial membrane proteins.2. The enzyme had a molecular weight equal to beef heart ATPase and was composed of five subunits with molecular weights of 56 200, 54 300, 33 500, 13 400 and 9500 respectively. 3. Isolated ATPase was labile while cold and was activated by the divalent cations Mn2+, Mg2+, Co2+ and Cd2+. The optimum ATP/Mg2+ ratio found was 1.58 and the enzyme had a maximum activity at pH 8.5; the Km was 220 micrometer. 4. The ATPase activity was 55% inhibited by aurovertin. The isolated enzyme enhanced the fluorescence of aurovertin, quenched by ATP and Mg2+ and enhanced by ADP. 5. Oligomycin sensitivity and cold stability of isolated ATPase was restored by its reconstitution with both brown adipose tissue and beef heart particles depleted of ATPase. 6. The results presented demonstrate that the low ATPase activity of brown adipose tissue mitochondria is due to a reduced content of ATPase.
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PMID:Purification and properties of mitochondrial adenosine triphosphatase of hamster brown adipose tissue. 14 14

A partially purified soluble ATPase (ATP phosphohydrolase, EC 3.6.1.3) from pea cotyledon mitochondria was characterized. Inhibition patterns with azide, NaF, and cold, and a stimulation by 2,4-dinitrophenol were typical of F1-ATPases from mammalian mitochondria. The enzyme hydrolysed GTP, ITP, and ATP, but not CTP, UTP, ADP, or IDP. ATPase and ITPase activities were strongly inhibited by ADP and to a lesser extent by IDP. Distinctive properties of the pea mitochondrial enzyme were activation by high concentrations of CaCl2 and stimulation by NaCl.
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PMID:Partial characterization of a soluble ATPase from pea cotyledon mitochondria. 14 76

The affinity label 5'-p-(fluorosulfonyl)benzoyl adenosine modifies rabbit muscle phosphofructokinase to the extent of one group/subunit. Modification appears to occur at a binding site specific for AMP, cyclic AMP, and ADP, i.e. those adenine nucleotides which are activators under conditions where regulatory kinetic behavior is obtained. The consequences of the modification are consistent with the model proposed previously for correlation between the pK of specific ionizable groups, regulatory kinetic behavior, ligand binding, and the reversible cold inactivation of the enzyme (Frieden, C., Gilbert. H. R., and Bock, P. E. (1976) J. Biol. Chem. 251, 5644-5647). Thus, the modification shifts the apparent pK of the essential ionizable groups from 6.9 to 6.4 at 25 degrees C, with the result that regulatory kinetic behavior at pH 6.9 and 25 degrees C is lost. Furthermore, the apparent affinity of a site (other than the active site) for ATP, as measured by ATP-dependent quenching of intrinsic protein fluorescence at pH 6.9 and 25 degrees C, is decreased by the modification. Regulatory kinetic behavior for both substrates is obtained with the modified enzyme at a lower pH, consistent with the downward shift in the pK of the ionizable groups, but sensitivity to cAMP activation is abolished by the modification. The loss of regulatory kinetic behavior upon modification of sulfhydryl groups does not appear to be the same as that due to modification by the affinity label.
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PMID:Rabbit muscle phosphofructokinase. Modification of molecular and regulatory kinetic properties with the affinity label 5'-p-(fluorosulfonyl)benzoyl adenosine. 14 61

Choleragen selectively incorporates 3H from [3H]NAD labeled on the adenosine moiety and not 14C from [14C]NAD labeled on the nicotinamide moiety. This reaction does not require protein in addition to choleragen. Incorporation of isotope does not proceed at 4 degrees, requires dithiothreitol, is stable after extensive washing with cold trichloroacetic acid, and is decreased 80% by boiling in trichloroacetic acid. Studies with the A and B subunits of choleragen show that the A subunit catalyzes ADP-ribosylation and serves as an acceptor protein. The B subunit does not show catalytic or acceptor activity. We conclude that choleragen and its A subunit catalyze the hydrolysis of NAD and the enzymatic transfer of ADP-ribose to the A subunit.
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PMID:Transfer of ADP-ribose from NAD to choleragen: a subunit acts as catalyst and acceptor protein. 20 56

The ATP-ADP exchange activity previously described in a membrane farction of Escherichia coli appeared after a cold osmotic shock according to Neu and Heppel ((1965) J. Biol. Chem. 240, 3685--3692) in the shock fluid. Membranes derived from shocked cells had no activity. The enzyme responsible for this activity has been purified 125-fold and catalyzed the transfer of a phosphoryl radical from ribonucleosidetriphosphates (NTPs) to ribonucleosidediphosphates (NDPs); this is, therefore, a non-specific nucleosidediphosphate kinase (ATP:nucleosidediphosphate phosphotransferase, EC 2.7.4.6). The activity required the presence of a divalent cation, Mg2+, Mn2+ or Ca2+ at a unity mol/mol ratio of nucleotide for maximal activation. The enzyme exhibited simple saturation kinetics with respect to the phosphate donor but inhibition by excess substrate was observed upon increasing phosphate acceptor. The kinetics of the reaction indicated an ordered bi-molecular ping-pong reaction mechanism. Differential heat sensitivity of the enzyme whether it is heated alone with ATP, ADP or Mg2+ opens possibilities to study different enzyme-substrate complexes.
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PMID:Nucleosidediphosphate kinase of Escherichia coli, a periplasmic enzyme. 21 26

1. It is known that extracellular Na+ ions, in low concentrations, inhibit Na+-ATPase activity in resealed red cell ghosts and that this inhibition is reversed by high concentrations of extracellular Na+. We have attempted to elucidate these actions of extracellular Na+ by investigating the dependence on Na+ concentration of (a) ATP-ADP exchange and Na+-ATPase activity both in native and in N-ethylmaleimide (NEM)-treated (Na+ + K+)-ATPase from pig kidney, and (b) the rate of hydrolysis of the phosphorylated kidney enzyme in the absence of K+ ions. 2. With the native enzyme, ATP-ADP exchange and Na+-ATPase activity showed similar responses to changes in Na+ concentration: a steep but S-shaped rise between 0 and 2.5 mM, a slight fall (exchange) or a plateau (ATPase) between 2.5 and 10 mM, and a roughly linear rise between 10 and 150 mM. With NEM-treated enzyme, the ATP-ADP exchange, which was greatly accelerated, showed no sign either of inhibition at intermediate Na+ concentrations or of the reversal of that inhibition at higher concentrations. The exchange rate increased with Na+ concentration in a smooth curve and was half-maximal at about 7 mM. 3. The effects, on ATP-ADP exchange, of changing the concentrations of ATP, ADP and Mg have also been investigated. With both native and NEM-treated enzyme, the interactions of ATP, ADP and Mg are complicated; they show that, for the reaction leading to ATP formation, either free ADP rather than MgADP is the substrate, or Mg2+ ions are inhibitory (or both). 4. Since NEM, in the conditions in which we have used it, is believed to act by inhibiting the conversion of an ADP-sensitive form of the phosphoenzyme (E1P) to an ADP-insensitive form (E2P), the absence of Na+ inhibition of ATP-ADP exchange in NEM-treated enzyme, together with the parallel effects of Na+ ions on the ATP-ADP exchange activity and on the Na+-ATPase activity of native enzyme, suggests that the inhibitory effect of external Na+ occurs after the conversion of E1P into E2P. 5. To test whether this inhibitory effect of Na+ reflected inhibition of the hydrolysis of E2P, we measured the rate of loss of incorporated 32P when enzyme, newly phosphorylated by [gamma32P]ATP, was squirted into a large volume of ice-cold solution containing 1,2-cyclohexylenedinitrilotetraacetic aicd (CDTA), unlabelled ATP and 0, 5 or 150 mM-Na+. The rate of loss of radioactivity from the membranes was least at 5 mM-Na+, about twice as great at 150 mM-Na+, and about 5 times as great at 20 microM (final) Na+. 6. An unexpected feature of the results was that the pattern of stimulation of ATP-ADP exchange in intact cells. If Na+ ions are absent externally, a different could be fitted better on the assumption that activation by internal Na+ occurs at two sites with equal affinities, than on the assumptions that activation occurs at a single site or at three sites with equal affinities.
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PMID:Sodium ions, acting at high-affinity extracellular sites, inhibit sodium-ATPase activity of the sodium pump by slowing dephosphorylation. 22 96


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