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)

Yeast phosphoglycerate kinase is irreversibly inactivated upon incubation with 5'-[p-(fluorosulfonyl)-benzoyl]-1-N6-ethenoadenosine (5'-FSB epsilon A), an analogue to the nucleotide substrate. Marked protection against inactivation occurs with MgATP, ATP, MgADP, ADP, and 3-phosphoglycerate, suggesting that a part of the catalytic center is modified. The time dependence of the inactivation is characterized by a nonlinear kinetic profile. Curve fitting of various models for ligand binding to the enzyme suggested a two-site model. Modification of one of the sites appears to protect the catalytically essential site from modification. Stoichiometric studies show that the relationship between moles of 5'-FSB epsilon A incorporated per mole of enzyme and the residual enzymatic activity also shows nonlinear behavior. An extrapolated value of 1.5 mol of bound label/mol of enzyme corresponds to complete inactivation. The apparent overall pseudo first-order rate constant for the reaction between phosphoglycerate kinase and 5'-FSB epsilon A, as well as the separate rate constants for the modification, exhibit saturation behavior with respect to the concentration of 5'-FSB epsilon A, indicative of a rapid reversible binding of the reagent to the enzyme prior to modification.
 ...
PMID:Affinity labeling of phosphoglycerate kinase by 5'-[p-(fluorosulfonyl)benzoyl]-1,N6-ethenoadenosine. 366 85

Feeding natural fats varying in contents of palmitate (16:0), stearate (18:0), oleate (18:1), and linoleate (18:2) to rabbits resulted in modulation of platelet phospholipid fatty acyl composition. Rabbits were fed high fat semipurified diets containing 2% corn oil (CO) + 18% CO, cocoa butter (CB) or milkfat (M) for periods of up to 300 d. Platelet phospholipid linoleate contents corresponded to diet levels with 18:2 highest in CO-fed rabbits and following the sequence CO greater than CB greater than M. Stearate was highest in CB-fed rabbits, corresponding to high 18:0 levels in CB, but palmitate levels were not affected by diet. Both CB and M-fed rabbits were higher than CO-fed rabbits in oleate. Though CO is highest in 18:2, the accepted 20:4 precursor, arachidonate was highest in M-fed rabbits. Adding cholesterol (0.2%) to the diets did not affect platelet phospholipid fatty acyl composition except to elevate 20:4 in M-fed rabbits. CO-fed rabbits showed uniquely high levels of tetracosadienoate (24:2). Fatty acyl composition data were essentially constant between 200 and 300 d on diet. Phospholipid fatty acyl unsaturation was apparently homeostatically controlled as mole percent unsaturate to saturate ratios were independent of diet. The observed homeostasis resulted in minimal diet influences on platelet membrane fluidity and ADP or collagen stimulated platelet aggregation. Platelet fluidity, determined by fluorescence polarization, was a function of oleate and linoleate contents of the cells. Cholesterol feeding generally lowered platelet fluidity and altered the dependence of fluidity on fatty acyl composition.
 ...
PMID:Influence of saturated and unsaturated fats on platelet fatty acids in cholesterol-fed rabbits. 382 74

Important advances have been made in recent years in the study of the structure of pyruvate kinase: the amino acid sequence of the enzymes from chicken muscle and yeast have been established and the three-dimensional structure of the cat muscle enzyme has been determined at 0.26 nm resolution. Work in our laboratory has shown that dialdehyde-ADP (oADP) can be used as an affinity label of rabbit muscle pyruvate kinase: if the enzyme is incubated with cold oADP in the presence of high ADP concentrations, dialyzed and then incubated with 14C-oADP, the enzyme inactivates and one mole of radioactive oADP incorporates per mole of enzyme subunit. A labeled peptide with a molecular weight of about 5900 has been purified from a tryptic digest of the modified enzyme. The first 26 residues of the peptide have been sequenced and this sequence is identical to a region in the chicken muscle enzyme and a peptide isolated from the bovine muscle enzyme specifically labeled with trinitrobenzenesulfonate. High homology is also found with a region of the yeast enzyme. All this suggests that the isolated peptide is part of the active site; the modified amino acid, probably a lysine, seems to be located in one of the alfa helices of domain A of the enzyme, according to the x-ray data.
 ...
PMID:Pyruvate kinase: studies on affinity labeling and active-site structure using the rabbit muscle enzyme. 383 41

The N-terminal formic acid fragment (FA1) of the N-[3H]ethylmaleimide-labeled and carboxymethylated bovine mitochondrial phosphate transport protein (PTPN*CM) has been purified and completely sequenced: NH2-Ala-Val-Glu-Glu-Gln-Tyr-Ser-Cys-Asp-Tyr10-Gly-Ser-Gly-Arg-Phe- Phe-Ile-Leu-Cys- Gly20-Leu-Gly-Gly-Ile-Ile-Ser-Cys-Gly-Thr-Thr30-His-Thr -Ala-Leu-Val-Pro-Leu-Asp- -Leu-Val40-Lys-Cys(N-[3H]ethylmaleimide)-Arg-Met-Gln-Val-Asp- COOH. By thermolysin digestion of FA1 and high-performance liquid chromatography isolation of the radioactive subfragment Leu39-Arg43, the sole N-ethylmaleimide-binding residue has been identified as Cys42. FA1 contains a high mole percentage of cysteine (8.5%) and shows silver staining anomaly. Its sequence reveals significant homology in the triplicated gene regions (Pro27,132,229) of the mitochondrial ADP/ATP carrier from beef heart and Neurospora crassa. The hydropathic profile suggests that FA1 contains a transmembrane segment (Phe15-Val40) with only one basic (His31) and one acidic (Asp38) residue. The presence of the phosphate transport protein gene among nuclear genes is suggested from a lack of significant homology between the reverse-translated FA1 (mitochondrial codons) and the bovine mitochondrial genome. The inhibitory action of N-ethylmaleimide on the phosphate transport mechanism is discussed.
 ...
PMID:Sequence of the N-terminal formic acid fragment and location of the N-ethylmaleimide-binding site of the phosphate transport protein from beef heart mitochondria. 406 97

The relation of cyclic 3',5'-adenosine monophosphate to platelet function has been studied by investigating the influence of this compound and of its N(6)-2'-0-dibutyryl derivative on platelet aggregation and other aspects of platelet behavior after demonstration of adenyl cyclase activity in disrupted platelets. Dibutyryl cyclic AMP inhibited platelet aggregation induced by ADP, epinephrine, collagen, and thrombin. Cyclic AMP was also inhibitory but was less effective. The platelet "release reaction" was also inhibited; specifically, there was inhibition of the induction of platelet factor 3 activity and of the release of labeled 5-hydroxytryptamine. Platelet swelling produced by ADP was not inhibited. The action of dibutyryl cyclic AMP did not result from contamination with 5'-AMP, nor was it attributable to production of 5'-AMP by plasma enzymes. Dibutyryl cyclic AMP was degraded to 2'-O-monobutyryl cyclic AMP and to cyclic AMP in plasma, but plasma exhibited no cyclic nucleotide phosphodiesterase activity, and the production of 5'-AMP did not occur. The in vitro effects of dibutyryl cyclic AMP were associated with uptake of the compound by platelets. Adenyl cyclase activity of platelet homogenates was demonstrated with production of 9.27 x 10(-11) (+/-2.62 x 10(-11)) mole cyclic AMP per min per 10(10) platelets. The activity was increased by NaF and by prostaglandin PGE(1) and was decreased by epinephrine. The effect of epinephrine was blocked by phentolamine but not by propanolol. Adenyl cyclase activity was also inhibited by collagen, 5-hydroxytryptamine, and thrombin. ADP, dibutyryl cyclic AMP, and cyclic AMP did not alter adenyl cyclase activity. These observations are consistent with the hypothesis that platelet aggregation is favored by a decrease in platelet cyclic AMP and inhibited by an increase in cyclic AMP.
 ...
PMID:Cyclic 3',5'-adenosine monophosphate in human blood platelets. II. Effect of N6-2'-o-dibutyryl cyclic 3',5'-adenosine monophosphate on platelet function. 432 65

1. Changes in the concentrations of ATP, ADP, AMP, IMP, creatine and phosphorylcreatine (PC) have been measured in frog sartorius muscles after different periods of isometric stimulation at 20 degrees C. The heat production was measured in parallel experiments with a thermopile of the Hill-Downing type.2. Muscles were either in O(2) and unpoisoned or in N(2) and poisoned with iodoacetic acid to prevent aerobic and glycolytic recovery processes.3. Poisoning did not appear to alter the heat production of these muscles and had little effect on the tension for up to 8 sec tetanus.4. The break-down of high-energy phosphates ( approximately P) during contraction was faster in the poisoned muscles. Normal muscles were thus able to resynthesize high energy phosphates during the contraction. The resynthesis began at its maximum rate; part of it was probably due to glycolytic activity.5. During the first 2 sec of contraction (poisoned muscles), the only net reaction was an hydrolysis of PC, with an apparent enthalpy change of -8.3 kcal/mole. During longer contractions, the PC hydrolysis was accompanied by a net ATP hydrolysis and appearance of AMP and IMP.6. For the first 2 sec of contraction in the poisoned muscles, the observed heat agreed with that expected from the observed chemical changes multiplied by their molar enthalpy changes. After 2 sec, the observed heat was greater than that expected. At 12 sec this excess was about 74 mcal/g. Possible explanations for this discrepancy are discussed.
 ...
PMID:Energy balance in frog sartorius muscle during an isometric tetanus at 20 degrees C. 475 78

1. The general characteristics and Na and K movements of L cells (derived from mouse epithelium) have been measured. Both cells grown in suspension (LS cells) and as a monolayer (L cells) were used.2. The volume of L cells was 1.2 x 10(-9) cm(3) and of LS cells 3.5 x 10(-9) cm(3); of this 82% was water.3. Electron micrographs showed the presence of numerous protrusions (filopodia) from both forms of the cell. These had the effect of increasing the surface area of the cell by 2-4 times over smooth cells of the same volume. On changing from the flattened to the spherical shape during trypsinization, the filopodia altered to maintain a constant V/A ratio.4. These cells contain K, about 170 m-mole/l. intracellular water and Na, 9 m-mole/l. intracellular water (L cells only) at 20 degrees C. The K fluxes are 1.9 p-mole/cm(2) sec for LS cells and 0.8 p-mole/cm(2) sec for L cells and the Na fluxes are 1.8 p-mole/cm(2) sec for L cells (expressed as per total cell surface (including filopodia)). If expressed as p-mole/cell per sec then L and LS cells have the same K flux.5. 10(-4)M ouabain reduces the K influx to half, indicating an insensitivity to the glycosides common to the species. In the prolonged presence of ouabain the cells come into a new steady state with a [K](1), of 140 and a [Na](1) of 20-30 m-mole/l. intracellular water, but a constant [Na + K](1).6. Both DNP (10(-3)M) and IAA (10(-4)M) are required for maximum inhibition of K uptake, as both aerobic and anaerobic metabolic pathways may be used to drive the pump.7. K removal decreases the Na efflux, and Na removal (eventually) decreases the K influx providing evidence for Na/K coupling.8. The cells contain 7.5 m-mole/litre intracellular water of ATP, a level some 15 times that of ADP.9. The Na pump in these cells is very similar to that found in other tissues in that (a) it requires K to work, (b) it is blocked by ouabain and metabolic inhibitors and (c) it transports three molecules of Na for each two molecules of K.
 ...
PMID:Effect of ouabain and metabolic inhibitors on the Na and K movements and nucleotide contents of L cells. 510 32

1. Adenylate kinase (EC 2.7.4.3) has been shown to be present in human plasma obtained by conventional means and the adenylate-kinase activities of plasma and of lysed and intact human platelets and erythrocytes have been measured at 37 degrees by sensitive spectrophotometric methods. 2. The activities found in plasma ranged from 2.7 to 22.9mumoles of ADP formed/min./l. and in lysed platelets and lysed erythrocytes mean values of 0.79 and 12.0mumoles of ADP formed/min./10(9) cells respectively were found. Intact platelets and erythrocytes showed little or no activity. 3. The apparent K(m) of plasma adenylate kinase for ADP was found to be 1.4-1.6mm. 4. The adenylate-kinase activity of plasma was correlated with the free haemoglobin present and the larger part of the activity could be accounted for by haemolysis occurring either during the withdrawal of the blood or in vivo. 5. Aggregation of platelets by ADP, collagen fibres or thrombin released up to 16% of the platelet adenylate kinase into the suspending medium. 6. Measurement of the rate of breakdown of 1.6mum-ADP in plasma gave values of about 0.1mmu-mole/min./ml. This was not increased by addition of sufficient erythrocyte lysate to increase the activity of plasma adenylate kinase five to ten times. 7. It was concluded that the activity of adenylate kinase found in plasma, even after aggregation of the platelets, is insufficient to account for the rate of breakdown of low concentrations of ADP usually observed, and that another enzyme is responsible for this process.
 ...
PMID:The adenylate kinase of human plasma, erythrocytes and platelets in relation to the degradation of adenosine diphosphate in plasma. 604 99

The effects of methylmercuric chloride, mercuric chloride, and phenylmercuric acetate (10(-6) - 10(-3) mole/liter) on thrombin-induced release of adenine nucleotides from washed pig platelets were investigated. The inhibitory effects of mercurials were always reached when the higher thrombin concentration (0.74 units NIH/ml) was used. Incubation of washed pig platelets with methylmercuric chloride caused a decrease of intracellular level of platelet ATP and statistically significant changes in ATP/ADP ratio.
 ...
PMID:Effects of mercurial compounds on adenine nucleotides of washed pig platelets. 621 73

In order to study the mechanism for activation of ATP hydrolysis by Mg2+, the stoichiometry of the high affinity calcium-binding sites with respect to each form of reaction intermediate of sarcoplasmic reticulum ATPase was determined at 0 degrees C and pH 7.0 in the presence and absence of added Mg2+ using the purified ATPase preparation. High affinity calcium binding to the enzyme-ATP complex and to ADP-sensitive (E1P) and ADP-insensitive (E2P) phosphoenzymes occurred with stoichiometric ratios of 2, 2, and 0, and 3, 3, and 1 in the presence and absence of added Mg2+, respectively. The results were interpreted to indicate that in addition to 2 mol of calcium bound to the transport sites of the ATPase, 1 mol of divalent cation, which is derived from the metal component of the substrate, the metal-ATP complex, remains bound to each mole of the enzyme at least until E2P is hydrolyzed. As activation of phosphoenzyme hydrolysis by Mg2+ was blocked by the low concentrations of Ca2+ used in the calcium binding experiments, it was concluded that it is the magnesium derived from MgATP that is responsible for rapid hydrolysis of the phosphoenzyme intermediate.
 ...
PMID:Effect of divalent cation bound to the ATPase of sarcoplasmic reticulum. Activation of phosphoenzyme hydrolysis by Mg2+. 622 21


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