INFLUENCE OF CALCIUM IONS ON THE MYOSIN-CATALYZED HYDROLYSIS OF ADENOSINE TRIPHOSPHATE

1958 ◽  
Vol 36 (6) ◽  
pp. 896-901 ◽  
Author(s):  
G. E. Pelletier ◽  
Ludovic Ouellet
Keyword(s):  
Reaction Mechanism ◽  
Stability Constants ◽  
Adenosine Triphosphate ◽  
Calcium Ions ◽  
Equilibrium Constants ◽  
Hydrogen Ion ◽  
Ion Concentrations ◽  
Calcium Complexes ◽  
Hydrolysis Of

The activation of the myosin-catalyzed hydrolysis of adenosine triphosphate by calcium ions has been studied at pH 7.5 over a range of temperature extending from 3° to 25 °C. There is evidence that the activation is due to the equilibrium formation of a complex between adenosine triphosphate and calcium ions.From such a reaction mechanism, values of equilibrium constants are reported for the binding of adenosine triphosphate to the myosin in the presence and in the absence of calcium ions, together with stability constants for the calcium complexes of both the adenosine triphosphate and the myosin – adenosine triphosphate. The influence of hydrogen-ion concentrations on these constants is indicated.

Some Characteristics of the Enzymes of the Pyloric Caeca of Cod and Haddock

1937 ◽  
Vol 3 (5) ◽  
pp. 473-485 ◽  
Author(s):  
W. W. Johnston
Keyword(s):  
Protease Activity ◽  
Room Temperature ◽  
Maximum Activity ◽  
Hydrogen Ion ◽  
Ammonium Salts ◽  
Ion Concentrations ◽  
Pyloric Caeca ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Partial Vacuum

Investigation of fish enzymes for leather bates reveals that those of the pyloric caeca show their greatest influence on casein and collagen at hydrogen ion concentrations of approximately pH 8. The protease showed its maximum activity towards casein at a temperature of 45 °C. Ammonium salts at certain concentrations increased the rate of hydrolysis of collagen by about 40 per cent, but had no like stimulating effect on the hydrolysis of casein. A comparison showed that pyloric caeca enzymes were just as satisfactory as commercial leather bates or hog pancreas. When the pyloric caeca are allowed to autolyse at room temperature, the protease activity is constant for the first 24 hours, declines rapidly during the next 80 hours, and slowly thereafter. The most suitable method for preparing a dried preparation was by evaporation under partial vacuum, which, however, is accompanied by some loss of activity.

THE HYDROLYSIS OF THE CONDENSED PHOSPHATES: III. SODIUM TETRAMETAPHOSPHATE AND SODIUM TETRAPHOSPHATE

1956 ◽  
Vol 34 (7) ◽  
pp. 969-981 ◽  
Author(s):  
Joan Crowther ◽  
A. E. R. Westman
Keyword(s):  
Phosphate Glass ◽  
Sodium Phosphate ◽  
Hydrogen Ion ◽  
Ion Concentrations ◽  
First Order ◽  
Condensed Phosphates ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Ph Range ◽  
Hydrolysis Of

The rates of hydrolysis of sodium tetrametaphosphate and tetraphosphate (in the presence of tetrametaphosphate) have been measured at 65.5 °C. over the pH range 2.5 to 13.3. Tetrametaphosphate anions hydrolyze to tetraphosphate which in turn hydrolyzes to triphosphate and orthophosphate and not to pyrophosphate. Thus the terminal oxygen bridges in the tetraphosphate and not the central one are attacked preferentially. The reactions were first order and acid catalyzed. The tetrametaphosphate hydrolysis was also base catalyzed with a minimum rate in solutions of pH approximately 7.5. The rate of hydrolysis of tetraphosphate was greater than triphosphate at the hydrogen ion concentrations studied. Hydrolysis of a sodium phosphate glass indicated that preferential attack on terminal oxygen bridges takes place also with higher polymers. However, trimetaphosphate is formed at the same time.

Extraction of strontium and barium salts by the nitrobenzene solution of dicarbolide in the presence of glymes

1985 ◽  
Vol 50 (3) ◽  
pp. 581-599 ◽  
Author(s):  
Petr Vaňura ◽  
Emanuel Makrlík
Keyword(s):  
Stability Constants ◽  
Organic Phase ◽  
Equilibrium Constants ◽  
Minor Role ◽  
Nitrobenzene Solution ◽  
Ligand Structure ◽  
Stability Constants Of Complexes ◽  
Separation Factors ◽  
The Stability ◽  
A Minor

Extraction of microamounts of Sr2+ and Ba2+ (henceforth M2+) from the aqueous solutions of perchloric acid (0.0125-1.02 mol/l) by means of the nitrobenzene solutions of dicarbolide (0.004-0.05 mol/l of H+{Co(C2B9H11)2}-) was studied in the presence of monoglyme (only Ba2+), diglyme, triglyme, and tetraglyme (CH3O-(CH2-CH2O)nCH3, where n = 1, 2, 3, 4). The distribution of glyme betweeen the aqueous and organic phases, the extraction of the protonized glyme molecule HL+ together with the extraction of M2+ ion and of the glyme complex with the M2+ ion, i.e., ML2+ (where L is the molecule of glyme), were found to be the dominating reactions in the systems under study. In the systems with tri- and tetraglymes the extraction of H+ and M2+ ions solvated with two glyme molecules, i.e., the formation of HL2+ and ML22+ species, can probably play a minor role. The values of the respective equilibrium constants, of the stability constants of complexes formed in the organic phase, and the theoretical separation factors αBa/Sr were determined. The effect of the ligand structure on the values of extraction and stability constants in the organic phase is discussed.

scholarly journals The acidity of muscle during maintained contraction

1922 ◽  
Vol 93 (654) ◽  
pp. 406-410
Keyword(s):  
Manganese Dioxide ◽  
Hydrogen Ion ◽  
Ion Concentrations

In 1913, I described a method for recording changes in hydrogen-ion concentrations in tissues, by means of a manganese dioxide electrode in combination with a calomel electrode (1). By this method it was shown that the acidity of muscle probably increased at the same time as, or slightly before, the tension increased, and that the acidity decreased as the muscle relaxed (2). In a paper, which appeared as this note was being prepared for publication, Ritchie states that he has been unable to detect a variation in acidity by the use of manganese dioxide electrodes. I am inclined to think that his failure is due to the injury to the muscles on insertion of wires into its substance. In my own experiments the wires rest on the surface of the muscle.

THE HYDROLYSIS OF MONOPHOSPHOINOSITIDE BY EXTRACTS OF BRAIN

1967 ◽  
Vol 45 (6) ◽  
pp. 853-861 ◽  
Author(s):  
W. Thompson
Keyword(s):  
Fatty Acids ◽  
Enzyme Activity ◽  
Calcium Ions ◽  
Brain Extract ◽  
Monovalent Cations ◽  
High Concentration ◽  
Diffusible Factor ◽  
Hydrolysis Of ◽  
The Brain ◽  
Long Chain

The hydrolysis of monophosphoinositide by soluble extracts from rat brain is described. Diglyceride and inositol monophosphate are liberated along with a small amount of free fatty acids. Hydrolysis of the lipid is optimal at pH 5.4 in acetate buffer. The reaction is stimulated by calcium ions or by high concentration of monovalent cations and, to a less extent, by long-chain cationic amphipathic compounds. Enzyme activity is lost on dialysis of the brain extract and can be restored by diffusible factor(s). Some differences in the conditions for hydrolysis of mono- and tri-phosphoinositides are noted.

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