Exploring mode of phosphoramidon and Aβ peptide binding to hECE-1 by molecular dynamics and docking studies

Human Endothelin converting enzyme (hECE-1) has been widely known for its involvement in hydrolyzing Aβ peptides at multiple sites. In the present study we have performed molecular dynamics (MD) simulation of crystal structure complex of hECE-1 and its inhibitor phosphoramidon with Zn ion to understand the dynamic behavior of active site residues. Root Mean Square Deviation (RMSD) results revealed that enzyme hECE-1 structure was highly stable throughout the simulation period. The L-leucyl-L-tryptophan moiety and N-phosphoryl moiety of phosphoramidon was found in the S1 and S2 pockets of hECE-1 respectively. The inhibitor was stabilized by hydrogen bonding interactions with residues Arg 145, Asn 566, Pro 731 and His 732 of hECE-1. Based on this information molecular docking of hECE- 1 crystal structure with three different structures of Aβ peptides has been performed. Zinc ion interacts with His 607(NE2), His 611(NE2), Glu 667 (OE1, OE2) and backbone oxygen atom of Phe 19 showing catalytic coordination between Aβ peptide and hECE-1. The unusual orientation of Aβ peptide residues affects hydrophobic interactions and hydrogen bonding network between hECE-1 and Aβ peptide. The molecular basis of amyloid beta peptide cleavage by hECE-1 could aid in designing enzyme based therapies to control Aβ peptide concentration in Alzheimer's patient.