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STRUCTURE OF LEUKOTRIENE A4 HYDROLASE D375N MUTANT
OverviewOverview
Leukotriene A4 (LTA4, 5S-trans-5,6-oxido-7,9-trans-11,14-cis-eicosatetraenoic acid) hydrolase, (LTA4H)/aminopeptidase is a bifunctional zinc metalloenzyme that catalyzes, the final and rate-limiting step in the biosynthesis of leukotriene B4, (LTB4, 5S,12R-dihydroxy-6,14-cis-8,10-trans-eicosatetraenoic acid), a, classical chemoattractant and immune modulating lipid mediator. Two, chemical features are key to the bioactivity of LTB4, namely, the, chirality of the 12R-hydroxyl group and the cis-trans-trans geometry of, the conjugated triene structure. From the crystal structure of LTA4H, a, hydrophilic patch composed of Gln-134, Tyr-267, and Asp-375 was identified, in a narrow and otherwise hydrophobic pocket, believed to bind LTA4. In, addition, Asp-375 belongs to peptide K21, a previously characterized, 21-residue active site-peptide to which LTA4 binds during suicide, inactivation. In the present report we used site-directed mutagenesis and, x-ray crystallography to show that Asp-375, but none of the other, candidate residues, is specifically required for the epoxide hydrolase, activity of LTA4H. Thus, mutation of Asp-375 leads to a selective loss of, the enzyme's ability to generate LTB4 whereas the aminopeptidase activity, is preserved. We propose that Asp-375, possibly assisted by Gln-134, acts, as a critical determinant for the stereoselective introduction of the, 12R-hydroxyl group and thus the biological activity of LTB4.
About this StructureAbout this Structure
1GW6 is a Single protein structure of sequence from Homo sapiens with ACT, YB, ZN, BES and IMD as ligands. Active as Leukotriene-A(4) hydrolase, with EC number 3.3.2.6 Structure known Active Site: BES. Full crystallographic information is available from OCA.
ReferenceReference
Leukotriene A4 hydrolase: selective abrogation of leukotriene B4 formation by mutation of aspartic acid 375., Rudberg PC, Tholander F, Thunnissen MM, Samuelsson B, Haeggstrom JZ, Proc Natl Acad Sci U S A. 2002 Apr 2;99(7):4215-20. Epub 2002 Mar 26. PMID:11917124
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