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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 3 (1980), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. An acid phosphatase is isolated and purified to homogeneity from sycamore cell walls. The enzyme, which has a molecular weight close to 100,000, is a glycoprotein and is most probably made up of one polypeptide chain only. Its amino acid composition has been determined. Although homogeneous to polyacrylamide gel electrophoresis under non-denaturing conditions, the enzyme preparation still contains protease traces that tend to split polypeptide chain in two fragments.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 3 (1980), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Purified acid phosphatase from sycamore cell walls is not activated by increasing the ionic strength of the reaction mixture. However activation occurs when the enzyme is bound to small cell wall fragments. The apparent activation of the bound enzyme by ions is paralleled by a decline of the substrate concentration C1/2, that results in half of the maximum rate. Above ionic strengths of about 0.05 the bound and solubilized enzyme forms behave in the same manner. Titration of cell wall fragments at different ionic strengths show that the local pH, inside the cell wall fragments, is lower than the pH in bulk solution. These results are explained in the light of poly-electrolyte theory. The negative charges of the cell walls generate an electrostatic potential that results in the attraction or repulsion of ions. The local concentration of organic phosphate (the substrate of the enzyme) is then lower than its concentration in bulk solution. This concentration difference explains that the value of C1/2, or of the apparent Km of the bound enzyme, is greater than the true Km of the solubilized enzyme. Increasing the ionic strength tends to equalize bulk and local ion concentrations, and therefore apparently activates the bound enzyme.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 943-953 
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enzymes are catalysts occurring in living cells. The aim of this paper is to describe some basic properties of enzymes and to understand on a physical basis how the intracellular milieu may control the kinetics of enzyme reactions. We shall therefore consider in succession some kinetic properties of enzymes in solution and the way cell surfaces and biological membranes control the dynamics of enzyme reactions. The choice of topics which have been selected in this paper is somewhat arbitrary and certainly reflects the tastes and the personal interests of the authors.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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