Effects of Magnesium Ions on Thermal Inactivation of Alkaline Phosphatase

2005 ◽  
Vol 24 (7-8) ◽  
pp. 479-485
Author(s):  
Ying Zhu ◽  
Xue-Ying Song ◽  
Wen-Hua Zhao ◽  
Ying-Xia Zhang
Keyword(s):  
Alkaline Phosphatase ◽  
Thermal Inactivation ◽  
Magnesium Ions

scholarly journals Chicken Intestinal Alkaline Phosphatase

1960 ◽  
Vol 43 (6) ◽  
pp. 1149-1169 ◽  
Author(s):  
M. Kunitz
Keyword(s):  
Alkaline Phosphatase ◽  
Zinc Ions ◽  
Magnesium Ions ◽  
Intestinal Alkaline Phosphatase ◽  
Reversible Inactivation ◽  
Higher Temperature ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Zn Ions ◽  
Denaturation Of Proteins

Purified chicken intestinal alkaline phosphatase is active at pH 8 to 9, but becomes rapidly inactivated with change of pH to 6 or less. Also, a solution of the inactivated enzyme at pH 4.5 rapidly regains its activity at pH 8. In the range of pH 6 to 8 a solution of purified alkaline phosphatase consists of a mixture of active and inactive enzyme in equilibrium with each other. The rate of inactivation at lower pH and of reactivation at higher pH increases with increase in temperature. Also, the activity at equilibrium in the range of pH 6 to 8 increases with temperature so that a solution equilibrated at higher temperature loses part of its activity on cooling, and vice versa, a rise in temperature shifts the equilibrium toward higher activity. The kinetics of inactivation of the enzyme at lower pH and the reactivation at higher pH is that of a unimolecular reaction. The thermodynamic values for the heat and entropy of the reversible inactivation and reactivation of the enzyme are considerably lower than those observed for the reversible denaturation of proteins. The inactivated enzyme at pH 4 to 6 is rapidly reactivated on addition of Zn ions even at pH 4 to 6. However, zinc ions are unable to replace magnesium ions as cocatalysts for the enzymatic hydrolysis of organic phosphates by alkaline phosphatase.

Phosphoester specificity of purified human liver alkaline phosphatase

1979 ◽  
Vol 57 (7) ◽  
pp. 1000-1007 ◽  
Author(s):  
L. E. Seargeant ◽  
R. A. Stinson
Keyword(s):  
Alkaline Phosphatase ◽  
Atpase Activity ◽  
Human Liver ◽  
Magnesium Ions ◽  
Calcium Dependent ◽  
Ph Values ◽  
Regulator Protein ◽  
Calcium And Magnesium ◽  
Hydrolysis Of ◽  
Calcium And Magnesium Ions

Kinetic parameters for the hydrolysis of a number of physiologically important phosphoesters by purified human liver alkaline phosphatase have been determined. The enzyme was studied at pH values of 7.0 to 10.0. The affinity of the enzyme for the compounds was determined by competition experiments and by their direct employment as substrates. Phosphodiesters and phosphonates were not hydrolysed but the latter were inhibitors. Calcium and magnesium ions inhibited the hydrolysis of ATP and PP1 and evidence is presented to show that the metal complexes of these substrates are not hydrolysed by alkaline phosphatase. A calcium-stimulated ATPase activity could not be demonstrated for the purified enzyme or the enzyme in the presence of a calcium-dependent regulator protein. Nevertheless, the influence of magnesium and calcium ions on the ATPase activity of alkaline phosphatase means that precautions must be taken when assaying for Ca2+-ATPase in the presence of alkaline phosphatase.The low substrate Km values and the hydrolysis which occurs at pH 7.4 mean that the enzyme could have a significant phosphohydrolytic role. However, liver cell phosphate concentrations, if accessible to the enzyme, are sufficient to strongly inhibit this activity.

scholarly journals STUDIES OF TWO TYPES OF ALKALINE PHOSPHATASE IN NUCLEI ISOLATED FROM THE LIVERS OF FED AND FASTED RATS BY A MODIFICATION OF THE BEHRENS TECHNIQUE

1955 ◽  
Vol 1 (4) ◽  
pp. 331-338 ◽  
Author(s):  
Arthur J. Emery ◽  
Alexander L. Dounce
Keyword(s):  
Alkaline Phosphatase ◽  
Rat Liver ◽  
Liver Cell ◽  
Aqueous Media ◽  
Slight Modification ◽  
Magnesium Ions ◽  
Rat Liver Nuclei ◽  
Liver Nuclei ◽  
The One ◽  
Fasted Rats

1. Rat liver nuclei were isolated from normal rats and rats fasted for 36 hours by a slight modification of the Behrens technique. 2. The nucleus of the rat liver cell contains two types of alkaline phosphatase. This confirms the previous findings on rat liver nuclei isolated in aqueous media. 3. The one type of alkaline phosphatase is not activated by magnesium ions, and this enzyme is very strongly bound to structural material of the nucleus. The other type of alkaline phosphatase is activated by magnesium ions, and this enzyme is probably free to diffuse from cytoplasm to nucleus and vice versa through the nuclear membrane. 4. Fasting caused a pronounced decrease of protein in general and of the alkaline phosphatase which is activated by magnesium ions from the nucleus of the rat liver cell, while the alkaline phosphatase that is not activated by magnesium was less affected.

The reactivation of milk alkaline phosphatase after heat treatment

1962 ◽  
Vol 29 (1) ◽  
pp. 21-35 ◽  
Author(s):  
R. L. J. Lyster ◽  
R. Aschaffenburg
Keyword(s):  
Heat Treatment ◽  
Alkaline Phosphatase ◽  
Simple System ◽  
Phosphate Esters ◽  
Magnesium Ions ◽  
Factors Affecting ◽  
Heat Stable ◽  
Reactivation Process ◽  
Low Concentrations ◽  
Β Lactoglobulin

SummaryA simple system was developed, consisting of a solution of β-glycerophosphate, β-lactoglobulin and magnesium ions, in which alkaline phosphatase isolated from milk became strongly reactivated following heat treatment for 45 sec in boiling water. From 10 to 30% of the original enzyme activity reappeared after incubation at 37°C. Variations in the components of the system, and factors affecting it, were studied. Salts of Hg, Zn and Cd inhibited reactivation at low concentrations.Milk which, after the same heat treatment, became reactivated to a much smaller extent (about 1%), was found to contain a dialysable, heat labile inhibitor whose presence is thought to be largely responsible for the low level of reactivation, though other factors, e.g. the suboptimal concentration of phosphate esters must be considered as contributory causes.Milk contains also a non-dialysable, heat stable activator of the reactivation process, capable of replacing β-lactoglobulin in the simple system and active at very low concentration, e.g. 0·2% (v/v).

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