Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.6.4.1 (myosin ATPase)
 1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Young rats fed a protein-deficient diet have elevated total triiodothyronine (T3) levels in spite of decreased skeletal muscle protein turnover. Interpretation of the thyroid status of these animals is complicated by increased T3 binding by serum proteins. Free T3 levels ranging from normal to low and decreased resting oxygen consumption have been reported. To investigate the thyroid status of animals fed a protein-free diet, ventricular myosin ATPase activity and isomyosin profile have been used as an index of thyroid hormone activity. The effect of the protein-free diet has been compared to a restricted high protein-low carbohydrate diet, which causes clear evidence of decreased thyroid hormone effect. After 28 d, calcium-activated myosin ATPase activity was 1.50 +/- 0.05 mumol Pi/(mg protein.min) in animals fed the basal diet, 1.16 +/- 0.03 mumol Pi/(mg protein.min) in animals fed the restricted high protein-low carbohydrate diet and 1.48 +/- 0.04 mumol Pi/(mg protein.min) in animals fed the protein-free diet. In addition, a shift in isomyosin content with the appearance of V2 and V3 isomyosins occurred with the restricted high protein-low carbohydrate diet but not the protein-free diet. The failure of the protein-depleted rats to decrease myosin ATPase activity and alter isomyosin content suggests that they are euthyroid.
J Nutr 1987 Dec
PMID:Comparison of the effect of a protein-free and restricted high protein-low carbohydrate diet on ventricular myosin ATPase activity and isomyosin profile in young rats: evidence that protein-depleted animals are euthyroid. 296 54

Dietary manipulations involving high carbohydrate feeding increase V1 cardiac myosin isoform expression in hormonally deficient rats. The purpose of this study was to determine if extremes in dietary carbohydrate availability could alter cardiac myosin isoform patterns in normal weanling and adult rats. Three and six weeks of dietary manipulations (either high or low carbohydrate diets) failed to change calcium-activated myofibril ATPase activity, calcium regulated myofibril ATPase activity, or the myosin isoform distribution in the adult. In contrast, a four week, high carbohydrate diet reduced calcium activated myosin ATPase activity by 33%, calcium regulated myofibril ATPase activity by 10%, and V1 isoform expression by 66% in weanling rats. Although the low carbohydrate diet caused no change in the myosin ATPase properties, it decreased V1 isoform expression by 17%. These results show that carbohydrate availability can alter cardiac myosin isoform expression in normal rats, but only at weanling age. The reason for this age-related contrast in response to dietary manipulations is unknown at this stage. The dietary manipulations may have acted directly on the heart by creating a state of malnutrition, or indirectly, by altering some developmental process which links maturation of the sympathetic nervous system with myosin isoform expression.
Mol Cell Biochem 1987 Dec
PMID:Differential effects of carbohydrate intake on cardiac myosin isoform expression in normal weanling and adult rats. 296 58

The myosin ATPase activity and myosin light chain composition in developing chick heart and skeletal muscles were studied and compared. Embryonic myosin was purified and characterized from day 7 to day 19 of embryogenesis. Embryonic cardiac myosin generally showed the same Ca2+-activated myosin ATPase activity level as the adult value. In comparison, pooled pectoralis and hindlimb skeletal muscles from day 10 through day 19 showed myosin ATPase activities that were all significantly less than the adult counterpart. The myosin light chain pattern of embryonic cardiac myosin remained relatively constant like the myosin ATPase activity, whereas developmental changes were observed in skeletal myosin light chains.
Mech Ageing Dev 1988 Dec
PMID:Myosin ATPase activity during avian cardiac and skeletal muscle development. 297 4

Regulatory light chain-a myosin kinase (aMK), which phosphorylates one of the myosin regulatory light chains, RLC-a, contained in the catch muscle of scallop, was also found to phosphorylate heavy chains of scallop myosin. After incubation of myosin isolated from the opaque portion of scallop smooth muscle (opaque myosin) with aMK in the presence of [gamma-32P]ATP, about 2 mol of 32P was incorporated per mol of the myosin. The radioactivity was mostly found in the heavy chain at 0.26 M KCl. The pH-activity curve and MgCl2 requirement for the heavy chain phosphorylation were similar to those for RLC-a phosphorylation. In contrast, the dependency of activity on KCl concentration was different from that for RLC-a. The heavy chain phosphorylation activity decreased with increase in KCl concentration up to 0.06 M, and then increased at concentrations over 0.06 M to a maximum at around 0.26 M KCl. This complicated profile probably reflects the solubility of myosin, and the phosphorylation site may be located in the rod portion insoluble at low KCl concentrations. Phosphorylation of heavy chain did not change the solubility of the opaque myosin molecule at all. The acto-opaque myosin ATPase activity in the presence of Ca2+ was found to be decreased to less than one-fourth by the heavy chain phosphorylation.
J Biochem 1988 Dec
PMID:Regulatory light chain-a myosin kinase (aMK) catalyzes phosphorylation of smooth muscle myosin heavy chains of scallop, Patinopecten yessoensis. 297 85

Adult rats treated with high doses of streptozocin became progressively more hyperglycemic during the first month of the diabetic condition. Treatment of these rats with the sulfonylurea glyburide halted, and in some cases, reversed this process in a high percentage of the diabetics. Associated with the glyburide-mediated improvement in fasting blood glucose levels was an increase in myocardial glucose utilization and lactate production. The stimulation of myocardial glucose utilization by insulin was greater in glyburide-treated hearts, indicating that the hyperglycemic agent increased insulin responsiveness. The sulfonylurea also partially restored insulin sensitivity to the normal range. In agreement with previous studies, myocardial mechanical function was significantly impaired in the diabetic heart. When treated with glyburide, the severity of the mechanical defect was significantly less. The sulfonylurea also promoted an increase in myosin ATPase activity and a shift in the myosin isozyme pattern in favour of the most active V1 form. These results imply that glyburide therapy can provide benefit to the diabetic heart by improving energy metabolism and promoting a shift in myosin towards the most active form.
Can J Physiol Pharmacol 1988 Dec
PMID:Effect of chronic sulfonylurea treatment on the myocardium of insulin-dependent diabetic rats. 314 10

After prolonged ischemia followed by reperfusion of the isolated rat heart, irreversible heart failure is associated with creatine kinase leakage from the cells. The possible implications of MM creatine kinase leakage from myofibrillar compartments on the contractile properties of ventricular muscle have been studied in control versus ischemic hearts. Total creatine kinase activity decreased in ischemic cells while creatine kinase and ATPase activities were not modified in isolated myofibrils. The efficiency of creatine kinase and phosphocreatine in the relaxation of rigor tension in skinned ventricular preparations was not changed after ischemia. Furthermore, neither the pCa/tension relationship nor the rate of tension development following length changes were modified by ischemia. These results show that the contractile properties of myofilaments as well as the functional coupling between myosin ATPase and creatine kinase are preserved in ischemic hearts suffering irreversible contractile failure.
Biochem Med Metab Biol 1987 Dec
PMID:Contractile properties and creatine kinase activity of myofilaments following ischemia and reperfusion of the rat heart. 343 83

The binding of Na+ and K+ by glycerinated muscle fibres was observed at reserve concentrations of NaCl in the medium. Under external concentrations of Na+ of K+ up to 0.4-0.5 mM, a constant fraction (0.15-0.25 mmoles/kg dry weight of the fibres) bound by glycerinated fibres was revealed. With the increase of NaCl or KCl concentration in the medium up to 10 mM the concentration of bound cations increased too. The parameters of Na+ and K+ sorption by glycerinated models were calculated. The values of Na+ and K+ binding limits were 4.4 and 1.8 mmole/kg dry weight of the fibres and those of affinity, 3.2 and 4.1 kcal/mol, respectively. The binding of one cation took place in conditions when its concentration was 10,000-20,000 fold less than that of the other cation. This points to the fact that Na+ and K+ binding is highly specific and is carried out by different centres. It is suggested that myosin ATPase is a substratum binding Na+ and K+ in glycerinated muscle fibres at reverse ratio concentrations of these cations in the medium.
Tsitologiia 1987 Dec
PMID:[Na+ and K+ binding by glycerinated muscle fibers with reciprocal cation concentrations in the medium]. 350 45

All skeletal muscle can produce roughly the same maximal cross-sectional force; however, the power (energy X time-1) required to develop and maintain that force increases with increasing contraction velocity. Thus the rate of muscle tension development may be of primary importance in setting the energy demand of contracting muscle. We have estimated the rate of muscle shortening during terrestrial locomotion in mammals as a function of body mass. The rate of muscle shortening of the knee extensors is much faster in small than large mammals, scaling in proportion to the -0.23 power of mass. This exponent suggests a constant body size-independent relation among skeletal muscle: O2 consumption, mitochondria content, myosin ATPase activity, and in vivo shortening velocity.
Am J Physiol 1985 Dec
PMID:Estimate of muscle-shortening rate during locomotion. 407 90

It is suggested that under physiological conditions (> 1 mM Mg(2+)) MgATP binds to myosin to form a chelate involving the two reactive sulfhydryl sites (SH(1) and SH(2)). The stability of the chelate structure results in marked inhibition of the myosin ATPase in the presence of millimolar magnesium ion. The inhibitory effect of magnesium ion can be eliminated chemically by blocking either the SH(1) or SH(2) site since this precludes formation of the chelate. In muscle, actin apparently behaves in a similar fashion in that its interaction with myosin causes a disruption of the chelate structure.
Proc Natl Acad Sci U S A 1973 Dec
PMID:Myosin ATP hydrolysis: a mechanism involving a magnesium chelate complex. 427 2

The steady-state kinetics of the K+, Ca2+, and Mg2+-activated adenosine triphosphatase (ATPase) activities of rabbit skeletal myosin were investigated in the substrate concentration range from 0.05 microM to 5 mM and found not to follow Michaelis-Menten kinetics but rather to display biphasic behavior. The Ca2+-ATPase activity of myosin chymotryptic subfragment-1 (S-1), which has only one active site, also exhibits biphasic kinetics, thus excluding the possibility that the biphasic behavior is caused by negative cooperativity between the two active sites of myosin. Myosin K+ and Mg2+-ATPase are both activated by 5'-adenyl methylenediphosphonate (AdoPP[CH2]P) in a competitive manner at high substrate concentrations; i.e. the maximal velocity observed at high substrate concentrations is independent of the AdoPP[CH2]P concentration. This result provides evidence for substrate activation via binding to a regulatory site. Pyrophosphate inhibits myosin ATPase in a competitive manner at low substrate concentrations and in an uncompetitive manner at high substrate concentrations, with the uncompetitive Ki being smaller than the competitive Ki; i.e. pyrophosphate binds more tightly to the effector site than to the active site.
Eur J Biochem 1980 Dec
PMID:Biphasic steady-state kinetics of myosin adenosine triphosphatase. Evidence for a substrate effector site. 610 32


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