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Evidence for essential histidine residues in bovine-liver mitochondrial monoamine oxidase

A Hiramatsu, S Tsurushiin, K T Yasunobu

    European Journal of Biochemistry
    |September 15, 1975
    PubMed

    Insights

    Ethoxyformic acid anhydride and photooxidation inactivate monoamine oxidase by reacting with histidine residues. Specific histidine residues were identified as essential for enzyme activity, crucial for understanding its function.

    Area of Science:

    • Biochemistry
    • Enzymology
    • Protein Chemistry

    Background:

    • Monoamine oxidase (MAO) is a critical enzyme in neurotransmitter metabolism.
    • Identifying essential amino acid residues is key to understanding enzyme mechanisms and developing inhibitors.

    Purpose of the Study:

    • To investigate the role of histidine residues in the activity of bovine hepatic monoamine oxidase.
    • To identify specific histidine residues essential for MAO function.

    Main Methods:

    • Enzyme inactivation using ethoxyformic acid anhydride.
    • Photooxidation in the presence of rose bengal.
    • Enzyme reactivation studies using hydroxylamine (NH2OH).

    Main Results:

    • Ethoxyformic acid anhydride inactivated MAO by reacting with approximately 6 histidine residues per 100,000 g of protein.
    • Photooxidation destroyed about 9 histidine residues per 100,000 g of protein.
    • In the presence of substrates (kynuramine or benzylamine), only 7 histidine residues were destroyed, indicating 2 essential histidine residues.

    Conclusions:

    • Histidine residues are crucial for the catalytic activity of monoamine oxidase.
    • At least two specific histidine residues are essential for bovine hepatic MAO function.

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