The Functional Groups of the Mg–Ca ATPase from Escherichia coli

1975 ◽  
Vol 53 (6) ◽  
pp. 658-665 ◽  
Author(s):  
Jan Ahlers ◽  
Doris Kabisch ◽  
Theodor Günther
Keyword(s):  
Escherichia Coli ◽  
Metal Ion ◽  
Experimental Error ◽  
Dissociation Constants ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
E Coli ◽  
Membrane Bound ◽  
Arginyl Residues

The influence of hydrogen ion concentration on binding and conversion of MgATP and CaATP by membrane bound and solubilized ATPase from Escherichia coli has been investigated. The reaction of enzyme (E), hydrogen ion (H+), and substrate (S) proceeds according to the following scheme, where Me is the metal ion and P is the product(s).[Formula: see text]Within experimental error, the results obtained with membrane-bound and solubilized ATPase are identical. Changing the concentration of Mg2+ ions or replacement of Mg2+ by Ca2+ ions alters the dissociation constants Kb, KHMeATP, and [Formula: see text]. The kinetics and experiments with group-specific inhibitors suggest that integrity for amino, imidazole, tyrosyl, carboxyl, and arginyl residues is required for activity of membrane-bound and solubilized E. coli ATPase.

THE HYDROLYSIS OF THE CONDENSED PHOSPHATES: II (A). THE ROLE OF THE HYDROGEN ION IN THE HYDROLYSIS OF SODIUM PYROPHOSPHATE: II (B). THE DISSOCIATION CONSTANTS OF PYROPHOSPHORIC ACID

1954 ◽  
Vol 32 (2) ◽  
pp. 174-185 ◽  
Author(s):  
J. D. McGilvery ◽  
Joan Pedley Crowther
Keyword(s):  
Dissociation Constants ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Rate Equations ◽  
Hydrogen Ion Concentration ◽  
Pyrophosphoric Acid ◽  
Condensed Phosphates ◽  
Anionic Species ◽  
Hydrolysis Of

The general rate equations for the hydrolysis of pyrophosphate anion proposed by Muus have been proved to be inapplicable over the pH range 2.0 to 11.0. A general rate equation is proposed which is based on the assumption that each anionic species of pyrophosphoric acid hydrolyzes at a rate which depends on its concentration, and that the only role of the hydrogen ion concentration is to determine the proportion of each species present in the solution. A mechanism for the hydrolysis of pyrophosphate anion is suggested.The dissociation constants of pyrophosphoric acid have been determined at 65.5 °C. for the concentration range 0.08 to 0.18 molar.

THE DEPENDENCE OF THE HYDROLYSIS OF DIAZOACETIC ESTER ON THE HYDROGEN ION CONCENTRATION

1953 ◽  
Vol 31 (5) ◽  
pp. 493-498 ◽  
Author(s):  
A. V. Willi ◽  
R. E. Robertson
Keyword(s):  
Experimental Error ◽  
Salt Effect ◽  
Sodium Perchlorate ◽  
Glass Electrode ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Diazoacetic Ester ◽  
Hydrolysis Of ◽  
Special Case

The catalytic constants of the H3O+ catalyzed hydrolysis of diazoacetic ester in aqueous solutions containing sodium perchlorate have been determined at three different ionic strengths. A spectrophotometric method was used to follow the rate. The results indicate a strong positive salt effect. Measurements at the ionic strength μ = 0.110 were carried out in the pH region from 1.97 to 5.19. For solutions containing less than 10−3 N perchloric acid the pH data were taken from measurements with a. glass electrode in the kinetic cell. Within the limits of experimental error no deviations from proportionality between rate and [H3O+] were found. This result is important in connection with our findings for the benzalaniline hydrolysis since it tests the methods applied and proves that the benzalaniline example with deviations from linearity between rate and [H3O+] is a special case. The diazoacetic ester hydrolysis is not catalyzed by acetic acid molecules.

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