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  • Title: Tryptophan 500 and arginine 707 define product and substrate active site binding in soybean lipoxygenase-1.
    Author: Ruddat VC, Mogul R, Chorny I, Chen C, Perrin N, Whitman S, Kenyon V, Jacobson MP, Bernasconi CF, Holman TR.
    Journal: Biochemistry; 2004 Oct 19; 43(41):13063-71. PubMed ID: 15476400.
    Abstract:
    There is much debate whether the fatty acid substrate of lipoxygenase binds "carboxylate-end first" or "methyl-end first" in the active site of soybean lipoxygenase-1 (sLO-1). To address this issue, we investigated the sLO-1 mutants Trp500Leu, Trp500Phe, Lys260Leu, and Arg707Leu with steady-state and stopped-flow kinetics. Our data indicate that the substrates (linoleic acid (LA), arachidonic acid (AA)), and the products (13-(S)-hydroperoxy-9,11-(Z,E)-octadecadienoic acid (HPOD) and 15-(S)-hydroperoxyeicosatetraeonic acid (15-(S)-HPETE)) interact with the aromatic residue Trp500 (possibly pi-pi interaction) and with the positively charged amino acid residue Arg707 (charge-charge interaction). Residue Lys260 of soybean lipoxygenase-1 had little effect on either the activation or steady-state kinetics, indicating that both the substrates and products bind "carboxylate-end first" with sLO-1 and not "methyl-end first" as has been proposed for human 15-lipoxygenase.
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