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Tryptophan 500 and arginine 707 define product and substrate active site binding in soybean lipoxygenase-1.

Biochemistry (2004-10-13)
Viola C Ruddat, Rakesh Mogul, Ilya Chorny, Cameron Chen, Noah Perrin, Stephanie Whitman, Victor Kenyon, Matthew P Jacobson, Claude F Bernasconi, Theodore R Holman
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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
15(S)-Hydroperoxy-(5Z,8Z,11Z,13E)-eicosatetraenoic acid, ~100 μg/mL in ethanol, ≥95%