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Human Leukotriene A4 Hydrolase in complex with Pro-Gly-Pro analogue and 4-(4-benzylphenyl)thiazol-2-amine
Structural highlights
FunctionLKHA4_HUMAN Epoxide hydrolase that catalyzes the final step in the biosynthesis of the proinflammatory mediator leukotriene B4. Has also aminopeptidase activity.[1] [2] [3] [4] [5] [6] [7] Publication Abstract from PubMedLeukotriene (LT) A4 hydrolase/aminopeptidase (LTA4H) is a bifunctional zinc metalloenzyme that catalyzes the committed step in the formation of the proinflammatory mediator LTB4. Recently, the chemotactic tripeptide Pro-Gly-Pro was identified as an endogenous aminopeptidase substrate for LTA4 hydrolase. Here, we determined the crystal structure of LTA4 hydrolase in complex with a Pro-Gly-Pro analog at 1.72 A. From the structure, which includes the catalytic water, and mass spectrometric analysis of enzymatic hydrolysis products of Pro-Gly-Pro, it could be inferred that LTA4 hydrolase cleaves at the N terminus of the palindromic tripeptide. Furthermore, we designed a small molecule, 4-(4-benzylphenyl)thiazol-2-amine, denoted ARM1, that inhibits LTB4 synthesis in human neutrophils (IC50 of approximately 0.5 muM) and conversion of LTA4 into LTB4 by purified LTA4H with a Ki of 2.3 muM. In contrast, 50- to 100-fold higher concentrations of ARM1 did not significantly affect hydrolysis of Pro-Gly-Pro. A 1.62-A crystal structure of LTA4 hydrolase in a dual complex with ARM1 and the Pro-Gly-Pro analog revealed that ARM1 binds in the hydrophobic pocket that accommodates the omega-end of LTA4, distant from the aminopeptidase active site, thus providing a molecular basis for its inhibitory profile. Hence, ARM1 selectively blocks conversion of LTA4 into LTB4, although sparing the enzyme's anti-inflammatory aminopeptidase activity (i.e., degradation and inactivation of Pro-Gly-Pro). ARM1 represents a new class of LTA4 hydrolase inhibitor that holds promise for improved anti-inflammatory properties. Binding of Pro-Gly-Pro at the active site of leukotriene A4 hydrolase/aminopeptidase and development of an epoxide hydrolase selective inhibitor.,Stsiapanava A, Olsson U, Wan M, Kleinschmidt T, Rutishauser D, Zubarev RA, Samuelsson B, Rinaldo-Matthis A, Haeggstrom JZ Proc Natl Acad Sci U S A. 2014 Mar 3. PMID:24591641[8] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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