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Membrane lipid physical state and modulation of the Na+,Mg2+-ATPase activity in Acholeplasma laidlawii B

J R Silvius, R N McElhaney

    Proceedings of the National Academy of Sciences of the United States of America
    |March 1, 1980
    PubMed

    Insights

    Membrane lipid properties significantly influence Na+,Mg2+-ATPase (ATP pyrophosphohydrolase) activity. The enzyme requires liquid-crystalline lipids to function, and its activity is modulated by lipid phase transitions.

    Area of Science:

    • Biochemistry
    • Membrane Biology
    • Enzyme Kinetics

    Background:

    • The Na+,Mg2+-ATPase (ATP pyrophosphohydrolase, EC 3.6.1.8) is a crucial enzyme in cellular energy metabolism.
    • Membrane lipid composition is known to affect the activity of membrane-bound enzymes.

    Purpose of the Study:

    • To investigate the impact of membrane lipid properties and phase transitions on Na+,Mg2+-ATPase activity in Acholeplasma laidlawii B.
    • To elucidate the relationship between lipid physical state and enzyme function.

    Main Methods:

    • Analysis of Arrhenius plots for enzyme activity across varying fatty acid compositions.
    • Differential thermal analysis of membrane lipid phase transitions.

    Main Results:

    • Na+,Mg2+-ATPase activity is restricted to liquid-crystalline lipid phases.
    • A significant heat capacity of activation (delta Cp++) was observed for the ATP hydrolytic reaction.
    • Enzyme inactivation occurs when boundary lipids undergo phase transitions linked to bulk lipid transitions.

    Conclusions:

    • Membrane lipid physical state is a critical determinant of Na+,Mg2+-ATPase activity.
    • The study suggests that complex Arrhenius plot shapes for membrane enzymes can reveal detailed information about enzyme behavior.

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