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:3.6.4.1 (myosin ATPase)
1,140 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Cross-reinnvervation of fast (extensor digitorum longus) and slow (soleus) twitch muscles of the rabbit showed essentially complete fast to slow and slow to fast conversion, respectively, 11-12 mo after surgery with respect to a number of physiological parameters including intrinsic shortening, velocity, and isometric twitch time to peak. There was pronounced bu incomplete biochemical conversion as judged by Ca2+ uptake by sarcoplasmic reticulum, myosin ATPase, alkali lability, and light chain complement. The question of trophic substances of neural origin is discussed in light of the fact that chronic stimulation for 15 wk of a fast muscle produces complete biochemical and physiological conversion to the slow type.
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PMID:Effect of cross-reinnervation on physiological parameters and on properties of myosin and sarcoplasmic reticulum of fast and slow muscles of the rabbit. 0 Apr 61

Structural and functional changes in myosin of fast muscles during early post-natal development were studied to seek correlations with well-known physiological changes in the contraction rate. The findings were as follows: 1. It is known that fetal fast muscle myosin contains three kinds of light chains. It was confirmed that their molecular weights were the same as those of adult fast muscle myosin, but different from those of adult slow muscle myosin. The amount of the smallest light chain, g3, was confirmed to increase markedly during the postnatal period. 2. The ATPase [EC3.6.1.3] activity of fetal fast muscle myosin (-1 day) was found to be about 50% of that of adult myosin. The pH-activity curve of fetal myosin ATPase was confirmed to be similar to that of adult myosin. 3. The rate of formation of the reactive myosin-phosphate-ADP complex, MADPP, was found not to change during post-natal development. 4. It was found that the rate of decomposition of MADPP in the presence of F-actin increased markedly during the post-natal period, and that the rate of decomposition of the complex of fetal mysoin was only 1/6 to 1/4 of that of adult myosin. The change in the actomyosin ATPase activity was found to be closely correlated with the increase in the g3 content during development.
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PMID:Developmental changes in the structure and kinetic properties of myosin adenosinetriphosphatase of rabbit skeletal fast muscle. 0 17

The flexibility of the tertiary structure around the active site of myosin ATPase [EC 3.6.1.3] was studied using the reactivity of two specific thiol groups, S1 and S2, as a structural probe. The following four maleimide derivatives were used as thiol-directed reagents: N-ethylmaleimide (NEM), N-(4-methoxy-2-benzimidazolyl methyl) maleimide (MBM), N-(p-(2-benzimidazolyl)phenyl)maleimide (BIPM) and N-(4-dimethyl-amino-3,5-dinitrophenyl)maleimide (DDPM). 1. All the maleimide derivatives used activated the Ca2+-ATPase activity and inhibited the EDTA-ATPase activity, like NEM, indicating that they modified S1. The rate of modification of S1 by NEM and BIPM increased with increasing pH, while that by DDPM decreased. BIPM simultaneously modified S1 and S2. 2. S1 showed much higher reactivity toward the maleimides, except for BIPM, than did N-acetylcysteine (N-Ac-Cys) a low molecular-weight model compound. The extremely small pKa value of S1, 6.28, accounted for this high reactivity. In addition, the ATP-induced increase in its reactivity inducated that S1 was in a buried state. Kinetic analysis showed that the teritiary structure around S1 at alkaline pH differed from that at acidic pH. 3. The apparent rate constant of S2-modification with NEM was approximately one seven-hundredth and one four-hundredth of those of S1 and N-Ac-Cys, respectively. Fluorimetric studies using BIPM revealed that S2 in the buried state was exposed upon adding ATP; this was compensated by the burying of some other thiol group(s) (Sp). Non-linearity of the Arrhenius plots of the reaction rate of S2 suggested that the S2 region of myosin had different conformations at high and low temperatures, the transition temperature being 10--15degrees. This non-linearity completely disappeared in the presence of Mg2+-ATP. On the other hand, Arrhenius plots for the thiols reactive to BIPM did not show non-linearity in the presence or absence of ATP.
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PMID:Thiols of myosin. IV. "Abnormal" reactivity of S1 thiol and the conformational changes around S2 thiol. 0 75

The interaction of magnesium-ADP with skeletal muscle heavy meromyosin has been studied by measuring the accompanying release of protons. Total pH changes of the order of 0.03 were involved, and measurements were performed with a discrimination of some ten-thousandths of a pH unit. At pH 8.0 and 25 degrees C about 0.5 mol of protons per mol of heavy meromyosin is released at saturation. A stoichiometry of binding close to 2 mol of ADP per mol of protein was found, with a binding constant, obtained from the proton release titration curve (pH 8.0, 25 degrees C), of 2 X 10(5) M-1. At 5 degrees C the release of protons per mole is slightly greater, and the binding constant is somewhat increased, reflecting a negative enthalpy of binding. Similar proton release behavior is observed in the presence of manganous ions in place of magnesium. The liberation of protons is thus unrelated to the temperature-dependent isomerization of myosin in the presence of substrate. Alkylation of a reactive thiol group (SH1) does not change the proton liberation at pH 8.0. From the pH dependence of proton release, the association constant of heavy meromyosin with magnesium-ADP at other pH values can be inferred and shows an appreciable rise as the pH increases. The pH-proton release profile also allows the pK of the ionizing groups perturbed by the ligand to be deduced. At least two groups ionizing above pH 7 and one below are involved. Their pK's in the unperturbed state are assigned as 8.5, 9.3, and about 6.6, respectively; they are displaced in the complex to about 8.0, 9.1, and 6.3. A relation to the pH-activity profile of myosin ATPase is indicated. The pH-proton release profile is somewhat changed when the SH1 group is alkylated. Measurements with potassium-ADP, in the absence of magnesium, show that at pH 8.0 there is no proton release but rather a sizeable proton absorption (about 0.5 mol of protons per mol of heavy meromyosin). The association constant derived from the titration curves (pH 8.0, 25 degrees C) is 3 X 10(4) M-1.
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PMID:An investigation of heavy meromyosin-ADP binding equilibria by proton release measurements. 1 88

The histochemical activities of succinic dehydrogenase (SDH) and Ca++-activated ATPase (pHs 7.4 and 9.4) were studied in the larval tail musculature of Rana japonica, Rana catesbeiana and Rana ornativentris. The ATPase reaction product was detected by both light and electron microscopy. 'Red' and 'white' muscle fibres, as distinguished by SDH, showed high and low Ca++-ATPase reaction, respectively, at pHs 7.4, 9.4 and following preincubation in cold K2-EDTA solution. The ultrastructural investigation of Ca++-ATPase reaction at pH 7.4 by the Ca++-citrophosphate technique demonstrated electron-dense reaction product in association with A, I and 'Z' bands, intermyofibrillar (SR) compartment and the mitochondrial inner chamber. However, Pb++ precipitation technique demonstrated Mg++-activated myosin ATPase activity at pH 9.2 ultrastructurally. The present histochemical data suggest that the anuran larval tail 'red' muscle fibres are possible 'slow,' and emphasize a possible lack of correlation between the speed of contraction with their ATPase activity. Moreover, 'red' muscle fibres of the anuran tai- musculature are not equivalent to 'Type I' fibres of higher chordates.
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PMID:Light and electron microscopic study of adenosine triphosphatase activity of anuran tadpole musculature. 2 41

Myosins isolated from individual human muscles (primarily normal muscles) were investigated with respect to their structural and catalytic properties. The results indicate unexpected elements of uniformity shared by the several myosins, such as a three-banded, electrophoretic pattern of light chains in sodium dodecylsulfate (SDS) gels and a low degree of alkaline lability. The pH activity profile and the effect of KCl on myosin ATPase activities were also found to be the same for the myosins from predominantly fast (e.g., vastus lateralis and rectus abdominis) and slow (e.g,, soleus and pectoralis minor) muscles. Coelectrophoretic experiments lend further credence to the interrelationship between human myosin light chains and the light chains of rabbit fast-muscle myosin. However, several kinds of circumstantial evidence, such as that derived from the study of myosin in nemaline myopathy, suggest that one shoould exercise caution in interpreting these results. On the other hand, human muscle myosins, like those of other mammalian species, can be divided into two main categories according to the peptide composition of tryptic heavy meromyosin (HMM) and the banding pattern of light meromyosin (LMM) paracrystals. These results, which are indicative of differences in the primary structure of the heavy chains, allow us to identify these heavy chains as the main site of heterogeneity among myosins in human mucles.
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PMID:Myosin polymorphism in human skeletal muscles. 3 46

The rate of enzymic reaction of ATP, ITP, GTP with myosin is studied in the presence of potassiu, ammonium and calcium ions in H2O--D2O solutions. There is no kinetic isotope effect of ITPase and GTPase reaction in the neutral pH region (VHVD = 1). The value VH/VD for the ATPase reaction in the pH range from 6.5 to 8.5 with all cations studied varies from 1.05 to 1.26. Such changes of myosin enzymic activity in D2O infer that small changes in the interaction of subunits is not the decisive one in the regulation of myosin ATPase. The equality of isotope effects in potassium salts and ammonium solution suggests that a specific effect of ammonium ion as a proton donor affects the ATPase reaction of myosin. The relationship between the value of isotope effect and D2O concentration in solution in non-linear. The shape of concentration curve suggests essential conformational changes of myosin during ATP hydrolysis.
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PMID:[Enzyme activity of myosin activated by different cations in a mixed H2O--D2O solvent]. 3 22

Cardiac myosin obtained from atria had a higher Ca2+-activated ATPase activity than did cardiac myosin from ventricles in various species of animals and in humans. The increased specific activity of Ca2+-activated adenosine triphosphatase (ATPase) of atrial myosin appeared to correlate with the level of the activity of ventricular myosin ATPase in the animal, since the same order in ATPase activity, as observed in ventricular myosins from various animals, was noted in atrial myosins. The enzymatic properties of atrial myosin also were characterized by no activation by N-ethylmaleimide, low activating energy, and a lower rate of inactivation at alkaline pH compared with the same properties of ventricular myosin. These findings suggest a difference in the myosin molecule at or near the active site, involving some sulfhydryl groups, between the two types of cardiac myosin. The Mg2+-activated ATPase activity, both in the presence and absence of actin (which is thought to be closely related to the basic contraction mechanism), also was enhanced in atrial myosin. Thus, the ATPase activities of atrial and ventricular myosins were different with special reference to the reaction pathway involving calcium and magnesium ions and appear to account for the difference in the velocity of contraction between the atria and the ventricles.
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PMID:Cardiac atrial myosin adenosine triphosphatase of animals and humans: distinctive enzymatic properties compared with cardiac ventricular myosin. 3 14

Muscle fibers are commonly classified histochemically into three types by the staining intensity for myosin ATPase combined with those for metabolic enzymes. Preincubation at pH 4.6 gives rise to three staining intensities of myosin ATPase which are also used for fiber typing. The two classification systems were compared by computer analysis of the individual staining profiles of over 2,500 fibers, and found not to be equivalent. The analysis showed metabolic heterogeneity among the fiber groups distinguished according to their differences in myosin ATPase.
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PMID:Metabolic heterogeneity of muscle fibers classified by myosin ATPase. 4 Sep 25

While modification of six lysyl residues causes a near maximal decrease in Ca2+, K+, and actin + Mg2+ -activated myosin ATPase activities in rabbit skeletal muscle myosin, it takes nearly twice this number of modified lysyl groups to cause a similar alteration in canine cardiac myosin where trinitrophenylation is nonspecific. It appears that there are several rapidly reacting lysyl residues in cardiac myosin; the active site of cardiac myosin is protected by ATP after modification of a limited number of these rapidly reacting lysyl groups. In both myosins, after a charge modification of these rapidly reacting lysyl groups, 6 in rabbit skeletal muscle myosin and 10 in canine cardiac myosin, there is a decrease in Ca2+, K+, and actin + Mg2+ -stimulation of myosin but an activation of Mg2+ -stimulated myosin ATPase activity, thus making actin + Mg2+ -stimulated myosin ATPase activity more like activation with K+ or Ca2+ as compared to activation with Mg2+ alone.
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PMID:Comparison of Mg2+ vs Ca2+, K+ and actin-activation of myosin after trinitrophenylation. 4 Dec 96


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