PDBsum entry 4mkt

Hydrolase

PDB id: 4mkt

Contents

Protein chain

608 a.a.

Ligands

28T

1V6

ACY ×2

Metals

_ZN

_YB ×2

Waters ×653

References listed in PDB file

Key reference

• Title: Binding of pro-Gly-Pro at the active site of leukotriene a4 hydrolase/aminopeptidase and development of an epoxide hydrolase selective inhibitor.
• Authors: A.Stsiapanava, U.Olsson, M.Wan, T.Kleinschmidt, D.Rutishauser, R.A.Zubarev, B.Samuelsson, A.Rinaldo-Matthis, J.Z.Haeggström.
• Ref.: Proc Natl Acad Sci U S A, 2014, 111, 4227-4232. [DOI no: 10.1073/pnas.1402136111]
• PubMed id: 24591641

Abstract

Leukotriene (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 Å. 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 ∼0.5 μM) and conversion of LTA4 into LTB4 by purified LTA4H with a Ki of 2.3 μM. In contrast, 50- to 100-fold higher concentrations of ARM1 did not significantly affect hydrolysis of Pro-Gly-Pro. A 1.62-Å 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 ω-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.