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)

The amount and the reaction capacity of the thiol groups in the sarcoplasmic reticulum containing up to 86% of Ca-ATPase were determined using 7-chloro-4-nitrobenzo-2-hydroxo-1,3-diazole (NBD-chloride). The total amount of SH-groups interacting with NBD-chloride is about 9 moles/10(5) g of protein as determined in the excess of NBD-chloride (750 micrometers). With respect to their sensitivity to NBD-chloride the SH-groups may be divided into two classes: slow and fast ones (5,3 and 3,5 moles/10(5) g of protein, respectively). The modification constants for the fast and slow SH-groups are 0,16 and 0,015min-1. ATP (30 micrometers) decreases the number of fast groups by 1 mole/10(5) g of protein. At higher concentrations of ATP (1--3 mM) the amount of fast SH-groups is decreased by 3 moles/10(5) g of protein, their modification rate constant being decreased 2-fold. ATP at concentration of 1 mM, decreases the rate constant for the Ca-ATPase inactivation by NBD-chloride from 0.68 down to 0,073 min-1, which coincides with the modification rate constant for fast SH-groups (0,071 min-1) under the same conditions. Ca2+ at concentration of 10(-4) M increases the amount of fast thiol groups by 1 mole/10(5) g of protein, the rate constant of their modification by NBD-chloride being increased 2-fold. A half-maximal effect was observed in the presence of 5.10(-7) M Ca2+ . Mg2+ did not affect the total amount of fast thiol groups; however, it decreased their modification rate constant.
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PMID:[Investigation of sarcoplasmic reticulum SH-groups]. 15 75

The temperature dependence and effects of sodium and potassium chloride on purified preparations of sarcolemmal Ca2+-activated ATPase were investigated. It was shown that within the concentration range of 0,1--1,0 M both salts have the same effect on the enzyme activity. A low ionic strength and concentration of the salts of 0,1 M the temperature maximum was 45 degrees and the shapes of temperature curves were the same. The Arrhenius plots showed a break at 16--19 degrees. The apparent activation energies were 27,3 kcal/mole below and 17,1 kcal/mole above the break point. At high ionic strength (0,5 M) the temperature maximum was observed at 40 degrees and the apparent activation energies decreased down to 18,0 kcal/mole below and 11,5 kcal/mole above the break point.
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PMID:[Effects of neutral salts and temperature on skeletal muscle sarcolemmal Ca-TPase]. 15 63

1. Conventional electrophysiological techniques were used to record from isolated rat phrenic nerve-hemidiaphragm preparations. After periods of rest (20 min) or nerve stimulation (7/sec for 20 min) the bathing medium of the preparation was removed and assayed for adenosine triphosphate (ATP) and adenosine diphosphate (ADP) using a sensitive modification of the firefly luciferase method (Silinsky, 1974). 2. In the presence of tubocurarine and normal (2 mM) calcium, fourteen periods of nerve stimulation (eight preparations) caused the appearance of ATP and/or ADP in amounts ranging from 28 to 641 p-mole. Experiments using carbachol (30 muM or 1 mM) suggested that this nucleotide efflux was not produced by a secondary action of released acetylcholine (ACh). 3. Stimulation of isolate phrenic nerve trunks at 7/sec for 20 min did not cause the efflux of ATP or ADP. 4. In solutions of normal osmotic pressure and reduced calcium concentrations (0-1 mM or 'calcium-free'), stimulation failed to release adenine nucleotide from non-contracting preparations. 5. Diaphragms were bathed in normal calcium and indirectly stimulated at 11/sec for 80-90 min in the presence of 5 times 10-minus 5 M hemicholinium-3. After all detectable signs of ACh release were eliminated, nerve stimulation failed to release ATP or ADP. 6. These results in conjunction with experiments on the hydrolysis of exogenous ATP suggest that ATP is released from the motor nerve ending and is subsequently degraded by enzymatic activity. It is also suggested that the released nucleotide may be derived from the cholinergic vesicle.
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PMID:On the association between transmitter secretion and the release of adenine nucleotides from mammalian motor nerve terminals. 16 62

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

The time course of binding of N-ethylmaleimide (NEM) to the SR was measured at pH 7.5 in the presence or absence of ATP or ADP. The following results were obtained. 1. Both in the presence and absence of nucleotide, the ATPase [EC 3.6.1.3] activity decreased linearly with increase in the amount of NEM bound to the fragmented sarcoplasmic reticulum (SR), and was inhibited almost completely by the binding of 2 moles of NEM per 10(5) g of the SR protein. 2. The amount of NEM incorporated into the ATPase (M.W.=105,000) was measured by SDS disc-gel electrophoresis. It was shown that the ATPase activity was inhibited almost completely by the binding of 2 moles of NEM per mole of ATPase. 3. The rate of binding of NEM to SR decreased by 30-40% in the presence of either ATP or ADP. The concentrations of both ATP and ADP for half-saturation were 0.1-0.2mM. 4. The effect of nucleotide on the rate of binding of NEM was not changed by the presence of Ca2+ and Mg2+ ions. Similar effects were also observed even when the SR membranes were solubilized with Triton X-100. It is suggested from these results that one or two SH groups are located in the active site of the SR ATPase, and that conformational changes are induced by the addition of ATP and ADP.
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PMID:Chemical modification of the Ca2+-dependent ATPase of sarcoplasmic reticulum from skeletal muscle. I. Binding of N-ethylmaleimide to sarcoplasmic reticulum: evidence for sulfhydryl groups in the active site of ATPase and for conformational changes induced by adenosine tri- and diphosphate. 18 70

About 10--20% of the total protein in the outer fiber fraction was solubilized by sonication in a solution containing 5 mM MES, 0.5 mM MgSO4, 1.0 mM EGTA, 1.0 mM GTP, and 0 or 50 mM KC1 at pH 6.7. The sonicated extract was shown by analytical centrifugation to consist largely of a 6 S component (tubulin dimer), having a molecular weight of 103,000, as determined by gel filtration, and possessing a colchicine-binding activity of 0.8 mole per tubulin dimer. The tubulin fraction failed to polymerize into microtubules by itself. Addition of a small amount of the ciliary outer fiber fragments or reconstituted short brain microtubules, however, induced polymerization, as demonstrated by viscosity of flow birefringence changes as well as light or electron microscopic observations. The growth of heterogeneous microtubules upon mixing outer fiber tubulin with DEAE-dextran-decorated brain microtubules was observed by electron microscopy. Microtubules were reconstituted from outer fiber tubulin without addition of any nuclei fraction when a concentrated tubulin fraction was warmed at 35degree. A few doublet-like microtubules or pairs of parallel singlet microtubules that were closely aligned longitudinally could be observed among many singlet microtubules. Unlike other fiber microtubules, the reconstituted polymers were depolymerized by exposure to Ca2+ ions, high or low ionic strength, colchicine, low temperature or SH reagents. No microtubules were assembled under these conditions.
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PMID:In vitro polymerization of flagellar and ciliary outer fiber tubulin into microtubules. 18 79

Dose of theophylline and caffeine which do not produce aortic arch anomalies in embryonic chicks have been shown to potentiate catecholamine-induced aortic arch malformations in that experimental animal. Theophylline (2.1 X 10(-5) mole per milliliter isotonic saline solution) potentiated the effective dose of norepinephrine more than 100 times. The greatest potentiation observed with epinephrine (2.5 X) was induced by 2.6 X 10(-5) mole caffeine. This study also demonstrated that both methylxanthines specifically induce aneurysms of the ascending aorta and complete absence (or nearly complete constriction) of the right ductus arteriosus. The incidences of these types of cardiovascular malformations proved to be dose dependent with theophylline a more potent teratogen than caffeine. The mobilization of calcium and/or cyclic nucleotide phosphodiesterase inhibition by the methylxanthines are suggested as significant actions in the potentiation of catecholamine-induced aortic arch anomalies.
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PMID:The effects of methylxanthines on catecholamine-stimulated and normal chick embryos. 19 58

A human skeletal actin.tropomyosin.troponin complex was phosphorylated in the presence of [gamma-32 P]ATP, Mg2+, adenosine 3':5'-monophosphate (cyclic AMP) and cyclic AMP-dependent protein kinase (protein kinase). Phosphorylation was not observed when the actin complex was incubated in the absence of protein kinase or 1 microM cyclic AMP. In the presence of 10(-7) M Ca2+ and protein kinase 0.1 mole of [32P]phosphate per 196 000 g of protein was incorporated. This was two-fold higher than the [32P]phosphate content of a rabbit skeletal actin complex but two-fold lower than that of a bovine cardiac actin complex. At high Ca2+, 5.10(-5) M, little change in the phosphorylation of a human skeletal actin complex occurred. Phosphoserine and phosphothreonine were identified in the [32P]phosphorylated actin complex. Polyacrylamide gel electrophoresis in sodium dodecyl sulfate showed that 60% of the label was associated with the tropomyosin binding component of troponin. The inhibitory component of troponin contained 16% of the bound [32P]phosphate. Increasing the Ca2+ concentration did not significantly decrease the [32P]phosphate content of the phosphorylated proteins in the actin complex. No change in the distribution of phosphoserine or phosphothreonine was observed. Half maximal calcium activation of the ATPase activity of reconstitute human skeletal actomyosin made with the [32P] phosphorylated human skeletal actin complex was the same as a reconstituted actomyosin made with an actin complex incubated in the absence of protein kinase at low or high Ca2+.
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PMID:Phosphorylation of an actin.tropomyosin.troponin complex from human skeletal muscle. 20 9

When myofibrils from rat hearts were dissolved in concentrated salt solutions and reprecipitated by dilution, they contained both protein kinase (partly cyclic 3':5'-AMP-dependent) and protein phosphatase activities. Troponin-I was the major protein to be phosphorylated by the endogenous myofibril-associated kinase and by added protein kinase. Approximately 1 mole of phosphate per mole of troponin-I was incorporated from radioactive ATP, but the extent of troponin-I phosphorylation could be varied experimentally. An inverse correlation was found between protein phosphorylation and the maximum Ca2+-stimulated myofibrillar Mg2+-ATPase activity, while the amout of calcium required for half-maximum activation was proportional to the extent of protein phosphorylation. The changes in Mg2+-ATPase activity produced in vitro by protein phosphorylation were reproduced in isolated perfused rat hearts treated for short periods with L-noradrenaline (10(-6)M). The changes in myofibrillar function brought about as the result of the phosphorlyation by cAMP-dependent protein kinase suggest that the contractile response is desensitized in order to cope with the rise in intracellular Ca2+ which results from the action of catecholamines on cardiac ventricular cells.
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PMID:Cardiac myofibrillar phosphorylation and adenosine triphosphatase activity. 22 75

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.
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PMID:The mitochondrial malic enzymes. I. Submitochondrial localization and purification and properties of the NAD(P)+-dependent enzyme from adrenal cortex. 23 89


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