Studies On The ACE Inhibitory Peptides With Phenylalanine C-terminus By 3D-QSAR?Activity Evaluation And Molecular Mechanism

Angiotensin converting enzyme(ACE)plays a vital role in regulation of blood pressure,and it is an ideal target in treatment of hypertension.ACE-inhibitory peptides are gaining considerable attentions because of their safty and easy absorption.In this paper,3D-QSAR CoMFA/CoMSIA models of ACE-inhibitory di-and tripeptides with phenylalanine C-terminus were built.According to the established models,potential ACE-inhibitory tripeptides were synthesized and verified their inhibitory activities in vitro.Furthermore,molecular dynamic simulations and nuclear magnetic resonance(NMR)were used to study the molecular mechanism of novel ACE-inhibitory tripeptide.The main research contents and results were as follows:In the first part,a dataset of 53 ACE-inhibitory di-and tripeptides with phenylalanine(F)C-terminus was collected to perform 3D-QSAR and molecular docking studies.The 3D-QSAR CoMFA/Co MSIA models with good predictive ability were established and the probable binding mode between inhibitors and ACE was obtained.Gly-Glu-Phe(GEF),Val-Glu-Phe(VEF),Val-Arg-Phe(VRF),and Val-Lys-Phe(VKF)were selected and synthesized to validate the constructed models.In the second part,the activities of four synthesized tripeptides were test by improved direct spectrophotometric method.The CoMFA/CoMSIA predicted p IC50 of GEF were closed to its experimental one,and the relative errors were 4.49% and 7.14%,respectively.The CoMSIA predicted and experimental p IC50 of VEF has the minimum relative error,1.08%.And the maximun relative error,9.87%,was the CoMFA predicted and experimental pIC50 of VRF.The result proved that the models were sufficiently reliable for predicting ACE-inhibitory peptides.In the third part,molecular dynamics simulations and 2D 1H-1H-NOESY spectroscopy were applied to study the conformations and hydrogen-bonding interactions of GEF-H2 O system and GEF-DMSO system.In aqueous solution,the GEF molecule could quickly change from folded state to extend state,and exist mostly in extend state.However,it preferred folded state in DMSO solution,and the extend state was hardly observed.The molecular dynamics simulations and 2D 1H-1H-NOESY show a good agreement with each other.In the forth part,molecular dynamics simulations were performed to study the interactions between GEF and ACE [C-domain(C-ACE)and N-domain(N-ACE)].The conformation of GEF molecule was more extend in the active site of C-ACE than it in N-ACE.The Lys475 residue of C-ACE was the vital factor that affected the binding of ligand and acceptor,while the Lys489 residue of N-ACE was the key factor that affected the binding of ligand and acceptor.The chelation between the zinc ion and ligand was the vital factor to stabilize the ligand-acceptor complexs.In this paper,a systematic method was established by combination of theory and experiment methods.The methods include the establishment of 3D-QSAR models for ACE-inhibitory peptides,design and synthesis of novel potential tripeptides,activity evaluation of novel tripeptides,and explaination of relationship between activity and structure on a micro level.This gives a support in studying and developing of ACE-inhibitory peptides.