Structural Origins for the Loss of Catalytic Activities of Bifunctional Human LTA4H Revealed through Molecular Dynamics Simulations

Abstract

Human leukotriene A4 hydrolase (hLTA4H), which is the final and rate-limiting enzyme of arachidonic acid pathway, converts the unstable epoxide LTA4 to a proinflammatory lipid mediator LTB4 through its hydrolase function. The LTA4H is a bi-functional enzyme that also exhibits aminopeptidase activity with a preference over arginyl tripeptides. Various mutations including E271Q, R563A, and K565A have completely or partially abolished both the functions of this enzyme. The crystal structures with these mutations have not shown any structural changes to address the loss of functions. Molecular dynamics simulations of LTA4 and tripeptide complex structures with functional mutations were performed to investigate the structural and conformation changes that scripts the observed differences in catalytic functions. The observed protein-ligand hydrogen bonds and distances between the important catalytic components have correlated well with the experimental results. This study also confirms based on the structural observation that E271 is very important for both the functions as it holds the catalytic metal ion at its location for the catalysis and it also acts as N-terminal recognition residue during peptide binding. The comparison of binding modes of substrates revealed the structural changes explaining the importance of R563 and K565 residues and the required alignment of substrate at the active site. The results of this study provide valuable information to be utilized in designing potent hLTA4H inhibitors as anti-inflammatory agents.

Weighted gene coexpression network analysis identifies specific transcriptional modules and hub genes related to intramuscular fat traits in chicken breast muscle

“…Previous studies have shown that polymorphism in ACSL4 is closely related to the IMF content in poultry . In addition, the HACD2 gene can catalyze the third step (dehydration) in the conversion of long‐chain FA to a very long‐chain FA, and thereby participate in saturated and monounsaturated FA elongation pathways; while the LTA4H gene is the final, rate‐limiting enzyme of the arachidonic acid pathway . Besides the above genes, we also found that the SLC27A1 gene is correlated to specific developmental changes in chicken tissue and facilitates IMF deposition via downregulation of FA oxidation .…”

“…50 In addition, the HACD2 gene can catalyze the third step (dehydration) in the conversion of long-chain FA to a very long-chain FA, and thereby participate in saturated and monounsaturated FA elongation pathways 51 ; while the LTA4H gene is the final, rate-limiting enzyme of the arachidonic acid pathway. 52 Besides the above genes, we also found that the SLC27A1 gene is correlated to specific developmental changes in chicken tissue 53 and facilitates IMF deposition via downregulation of FA oxidation. 4 Thus, these results in this study provide a basis for further study of the molecular regulation mechanism of specific FA metabolism in chicken IMF.…”

Substrate-dependent modulation of the leukotriene A4 hydrolase aminopeptidase activity and effect in a murine model of acute lung inflammation

“…The structures also reveal that Asp375, a key residue for argininyl-tripeptide hydrolysis, forms hydrogen bonding interactions with the guanidinium group of arginine to stabilize the N-terminal arginine residue and position the tripeptide for hydrolysis within the AP active site 28 , 31 . In addition, Arg563 and Lys565 are key residues for tripeptidase function as they cooperate with each other for strong alignment of the substrate at the binding site 32 . The crystal structure of [E296Q]LTA 4 H in complex with Arg-Ser-Arg (PDB ID: 3B7S) shows that the N-terminal arginine points toward Gln136 31 .…”

A comparative molecular dynamics study of thermophilic and mesophilic β-fructosidase enzymes

“…Several authors have reported a positive correlation between thermostability and protein rigidity [35][36][37][38], although there are no few examples of thermophilic proteins showing higher overall flexibility than their mesophilic counterparts at both low and high temperatures [35,[39][40][41][42].…”