Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.6.1.3 (ATPase)
65,361 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recent results suggest consideration of a new concept for oxidative phosphorylation in which a prime function of energy is to bring about release of ATP formed at the catalytic site by reversal of hydrolysis. Data with submitochondrial particles include properties of an uncoupler insensitive Pi=HOH exchange, a rapid reversible formation of bound ATP in presence of uncouplers, and predictable patterns of 32-Pi incorporation into ATP in rapid mixing experiments. ADP is confirmed as the primary Pi acceptor in mitochondrial ATP synthesis, but with chloroplasts ADP is also rapidly labeled. Other findings with pyrophosphatase and with transport ATPase harmonize with the new concept. Measurements of the reversal of ATP cleavage and binding by myosin suggest that oxygen exchanges result from reversible cleavage of ATP to ADP and Pi at the catalytic site and that the principal free energy change in ATP cleavage occurs in ATP binding. Reversal of conformational changes accompanying ATP binding and cleavage is proposed to drive the actin filament in contraction. Thus energy transductions linked to ATP in both mitochondria and muscle may occur primarily through protein conformational change.
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PMID:Coupling of "high-energy" phosphate bonds to energy transductions. 12 70

1. The (Na++K+)-ATPase of red cell membranes is unable to hydrolyse ATP-analogues in which the oxygen atom linking the beta- and gamma-phosphate groups is replaced by a minusCH2minus or minusNH-bridge. 2. In resealed ghosts both these ATP-analogues support K:K exchange but not Na:K exchange. ATP supports both modes of operation of the sodium pump, whereas neither occurs without any nucleotide. 3. These results support the hypothesis that ATP is needed as a cofactor for K:K exchange to occur, and make it extremely unlikely that phosphorylation from ATP is involved.
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PMID:The interaction of ATP-analogues possessing a blocked gamma-phosphate group with the sodium pump in human red cells. 12 51

When ATP binds to myosin in the presence of Mg2+ there follows a rapid cleavage reaction to yield a myosin-product complex whose breakdown is rate-limiting in the overall adenosine triphosphatase reaction at 21 degrees and pH 8.0. Recent kinetic studies on this system have led to the proposal that the cleavage of ATP bound to myosin is reversible. This conclusion is based in part on the observation that when ATP is mixed with an excess of myosin active sites a small amount of tightly bound ATP exists whose life-time coincides with that of the myosin-product complex and implies these two species are in equilibrium during their decay. Previous oxygen exchange studies have shown that phosphate released as free product contains more than one oxygen atom from water. A rapid equilibration between myosin-bound ATP and a myosin-products complex can account for the extra water oxygen incorporation of the product phosphate. Such a model requires that the gamma-phosphoryl group of the bound ATP also exchanges its oxygen atoms with water. Results presented in this paper show that protein-bound ATP labeled in the three terminal oxygen atoms of the gamma-phosphoryl group with 18O exchanges about 75% of its label within 2 s of binding to the active site of myosin. This result provides chemical evidence for a model in which bound ATP undergoes a reversible reaction with water. Incomplete exchange may arise from kinetic and/or structural restraints on the mechanism and plausible models are discussed.
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PMID:Oxygen exchange in the gamma-phosphoryl group of protein-bound ATP during Mg2+-dependent adenosine triphosphatase activity of myosin. 12 49

Muscle samples were obtained from the gastrocnemius of 17 female and 23 male track athletes, 10 untrained women, and 11 untrained men. Portions of the specimen were analyzed for total phosphorylase, lactic dehydrogenase (LDH), and succinate dehydrogenase (SDH) activities. Sections of the muscle were stained for myosin adenosine triphosphatase, NADH2 tetrazolium reductase, and alpha-glycerophosphate dehydrogenase. Maximal oxygen uptake (VO2max) was measured on a treadmill for 23 of the volunteers (6 female athletes, 11 male athletes, 10 untrained women, and 6 untrained men). These measurements confirm earlier reports which suggest that the athlete's preference for strength, speed, and/or endurance events is in part a matter of genetic endowment. Aside from differences in fiber composition and enzymes among middle-distance runners, the only distinction between the sexes was the larger fiber areas of the male athletes. SDH activity was found to correlate 0.79 with VO2max, while muscle LDH appeared to be a function of muscle fiber composition. While sprint- and endurance-trained athletes are characterized by distinct fiber compositions and enzyme activities, participants in strength events (e.g., shot-put) have relatively low muscle enzyme activities and a variety of fiber compositions.
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PMID:Skeletal muscle enzymes and fiber composition in male and female track athletes. 12 49

Sarcolemmal Ca++-ATPase, Mg++-ATPase, and (Na+-K+)-ATPase activities were increased in late stages of heart failure in myopathic hamsters (BIO 14.6) without any changes in the adenylate cyclase activity. On the other hand, these hamsters at early and moderate stages of heart failure showed depressions in mitochondrial calcium binding and uptake and microsomal calcium binding. Sarcolemmal (Na+-K+)-ATPase was decreased in failing hearts because of substrate lack, oxygen lack, and perfusion with Ca++-free, Na+-free, or K+-free medium. Both Mg++-ATPase and Ca++-ATPase activities of sarcolemma did not change on perfusing the hearts with substrate-free, hypoxic, Na+-free, or K+-free medium. Adenylate cyclase activity decreased on substrate-free or Ca++-free perfusion. Intracellular calcium overload produced by perfusing the hearts with medium containing calcium after Ca++-free perfusion was associated with decrease in all the sarcolemmal-bound enzyme activities. All types of failing hearts employed in this study showed a dramatic shift in the electrolyte composition. Failure of the cardiac muscle to generate contractile force on treatment with trypsin was associated with defects in the functions of sarcolemma, mitochondria, and sarcoplasmic reticulum, whereas such an effect on treatment with phospholipase C was limited to alterations in the activities of sarcolemma. The data suggest that abnormality at the level of sarcolemma plays an important role in the pathogenesis of heart dysfunction; however, the degree and direction of alterations in the sarcolemmal functions seem to be dependent upon the type of heart failure.
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PMID:Role of sarcolemmal changes in cardiac pathophysiology. 13 Jun 63

The effect of vibration (vibration level of 130 dB at a frequency of 2 Hz; 108, 118, and 105 dB at frequencies of 32, 63 and 125 Hz, respectively) combined with the noise at mid- and low-frequencies (sound pressure level of 85 dBA) was studied as applied to oxidative phosphorylation in mitochondria from skeletal muscles of the rats exposed to a single action of the mentioned factors, for a fortnight and for a month. A certain separation of oxidation and phosphorylation was observed after a fortnight action of the studied factors. The expressed changes in the process of oxidative phosphorylation were detected after the vibration-noise effect for a month. A considerable decrease of the P/O coefficient (almost twice as compared to the control one) occurs when oxygen uptake by mitochondria is intensified (1.9 times) and their phosphorylation activity is lower (by 61.5%). This is accompanied by a rise (by 2.65 times) of Mg2+-activated ATPase of mitochondria and by a deficit of adenylic system components (ATP, ADP, AMP) in the muscular tissue homogenate.
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PMID:[Oxidative phosphorylation in rat skeletal muscles in dynamics of vibration-noise effect]. 13 Jul 5

Different antiarrhythmic agents such as quinidine, procaine amide, and lodocaine at 1 mM concentrations were found to depress the ability of an isolated perfused rat heart to generate contractile force. Quinidine, but not procaine amide or lidocaine, decreased calcium uptake by both mitochondrial and microsomal fractions at different concentrations of calcium. The mitochondrial phosphorylation rate, respiratory control index, and state 3 oxygen consumption, but not ADP:O ratio and state 4 oxygen consumption, were depressed by only quinidine. None of these agents had any effect on myofibrillar Mg2+-ATPase or Ca2+-stimulated ATPase activities. On the other hand, sarcolemmal Mg2+-ATPase and Ca2+-ATPase activities, but not Na+-K+-ATPase activity, were increased by all these drugs. The sarcolemmal adenylate cyclase (EC 4.6.1.1) activity was decreased by quinidine only. These results suggest some similarities and differences in the sites of action of quinidine, procaine amide, and lidocaine within the myocardium.
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PMID:Subcellular and functional effects of quinidine, procaine amide, and lidocaine on rat myocardium. 13 Sep 65

13 male subjects were studied and placed in 3 groups. Each group exercised one leg with sprint (S), or endurance (E) training and the other leg oppositely or not at all (NT). Oxygen uptake (Vo2), heart rate and blood lactate were measured for each leg separately and for both legs together during submaximal and maximal bicycle work before and after 4 weeks of training with 4-5 sessions per week. Muscle samples were obtained from the quadriceps muscle and assayed for succinate dehydrogenase (SDH) activity, and stained for myofibrillar ATPase. In addition, eight of the subjects performed after the training two-legged exercise at 70% Vo2 max for one hour. The measurements included muscle glycogen and lactate concentrations of the two legs as well as the blood flow and the a-v difference for O2, glucose and lactate.
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PMID:The nature of the training response; peripheral and central adaptations of one-legged exercise. 13 82

The relation between Na-k-ATPase activity in homogenates of rat kidney and oxygen consumption in kidney slices was studied by employing different physiological maneuvers known to change the activity of renal Na-K-ATPase. Treatment of euthyroid rats with 3,5,3'-triiodo-1-thyronine increased Na-K-ATPase activity, sodium-dependent oxygen consumption (QO2[t]), and para-aminohippurate (PAH) accumulation by kidney slices without changing glomerular filtration rate or net sodium reabsorption by the intact kidney. Treatment with methylprednisolone also increased Na-K-ATPase, QO2[t], and PAH transport. Chronic potassium loading, on the other hand, increased renal Na-K-ATPase to the same degree as the first two procedures, but QO2[t] and PAH accumulation were unchanged. Partial nephrectomy induced an increase in the activity of Na-K-ATPase in homogenates of the remaining kidney fragment, but QO2[t] did not change significantly and PAH uptake was unaltered. An increase in the activity of Na-K-ATPase in kidney homogenates is therefore not necessarily associated with a parallel change in oxygen consumption by the intact cell.
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PMID:Relation between Na-K-ATPase activity and respiratory rate in the rat kidney. 13 22

Natriuresis occurs in the immediate postnephrectomy period. Yet in the days and weeks that follow, increased Na-K-ATPase (sodium-potassium activated adenosine triphosphate) activity, oxygen consumption and sodium reabsorption occur. Increased sodium reabsorption probably occurs early postuninephrectomy but is obscured by passive hemodynamic and physical-chemical factors that induce natriuresis. These factors were controlled in isolated canine kidneys perfused with normal and twenty-four-hour postuninephrectomized blood. A substance that increases sodium reabsorption and glomerular filtration rate in the kidneys perfused with uninephrectomized blood was demonstrated. The relationship between this and a hormonal substance that induces compensatory renal hypertrophy is unknown. The use of this hormone for treatment of renal failure is discussed.
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PMID:Increased sodium reabsorption postuninephrectomy: evidence for a humoral factor. 13 92


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