J. O’Sullivan

Trinity College Dublin, Dublin, L, Ireland

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Publications (2)6.1 Total impact

  • Source
    A. Olivieri, K. Tipton, J. O’Sullivan
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    ABSTRACT: Semicarbazide-sensitive amine oxidase (EC 1.4.3.6) acts as a vascular-adhesion protein (VAP-1), mediating the adhesion of lymphocytes to vascular endothelial cells under inflammatory conditions. The relationship between the adhesive and the enzymatic functions of SSAO have not yet been fully defined. Previous studies from this laboratory showed aminohexoses, which were neither substrates nor direct inhibitors of SSAO, bound to the enzyme as reversible inhibitors in the presence of H2O2 generated during substrate oxidation. The possibility that surface l-lysine could act similarly has been investigated in the present study. The presence of l-lysine during the oxidation of benzylamine resulted in time- and dose-dependent inhibition of SSAO activity, in a process that was dependent on the H2O2 formed during benzylamine oxidation. The possible implications of this in terms of the therapeutic uses of lysine are discussed. Keywords: Benzylamine, semicarbazide-sensitive amine oxidase, hydrogen peroxide (H2O2), inhibition
    Journal of Neural Transmission 01/2007; 114(6):747-749. · 3.05 Impact Factor
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    ABSTRACT: Amine oxidase substrates such as benzylamine and methylamine have been shown to stimulate glucose uptake by increasing the recruitment of the glucose transporter GLUT4 from vesicles within the cell to the cell surface. Inhibition of this effect by the presence of semicarbazide and catalase led to the suggestion that the process is mediated by the H2O2 produced in the oxidation of these amines. Tyramine, which is a substrate for both MAO and SSAO, can also stimulate this process and in that case both MAO and SSAO inhibitors attenuate the effect. Benzylamine does not occur physiologically and tyramine is normally present in only very low amounts. We have suggested that adrenaline, which also stimulates glucose metabolism through adrenoceptors, may act as the physiological substrate for GLUT4 recruitment. It is a substrate for MAO but not SSAO. However, oxidation of adrenaline by MAO releases both H2O2 and methylamine for further oxidation by SSAO. In order to gain a fuller understanding of this process we have performed simulation studies that may be used to assess the contributions of the amine oxidases to the process under a variety of conditions. The results are consistent with the experimentally observed behaviour. This approach not only helps to establish the feasibility of this process but also allows behaviour prediction and the identification of further experimental approaches. Keywords: Adrenaline, glucose transport, GLUT4, hydrogen peroxide (H2O2), methylamine, monoamine oxidase, semicarbazide-sensitive amine oxidase
    Journal of Neural Transmission 01/2007; 114(6):783-786. · 3.05 Impact Factor

Publication Stats

9 Citations
6.10 Total Impact Points

Institutions

  • 2007
    • Trinity College Dublin
      • School of Biochemistry and Immunology
      Dublin, L, Ireland