A novel angiotensin I-converting enzyme inhibitory peptide derived from the trypsin hydrolysates of salmon bone proteins.

Thanakrit Kaewsahnguan,Aphichart Karnchanatat,Piroonporn Srimongkol,Tanatorn Saisavoey,Sajee Noitang,Onrapak Reamtong,Papassara Sangtanoo,Kiattawee Choowongkomon,Shashi Kant Bhatia

doi:10.1371/journal.pone.0256595

Abstract

When fish are processed, fish bone becomes a key component of the waste, but to date very few researchers have sought to use fish bone to prepare protein hydrolysates as a means of adding value to the final product. This study, therefore, examines the potential of salmon bone, through an analysis of the benefits of its constituent components, namely fat, moisture, protein, and ash. In particular, the study seeks to optimize the process of enzymatic hydrolysis of salmon bone with trypsin in order to produce angiotensin-I converting enzyme (ACE) inhibitory peptides making use of response surface methodology in combination with central composite design (CCD). Optimum hydrolysis conditions concerning DH (degree of hydrolysis) and ACE-inhibitory activity were initially determined using the response surface model. Having thus determined which of the salmon bone protein hydrolysates (SBPH) offered the greatest level of ACE-inhibitory activity, these SBPH were duly selected to undergo ultrafiltration for further fractionation. It was found that the greatest ACE-inhibitory activity was achieved by the SBPH fraction which had a molecular weight lower than 0.65 kDa. This fraction underwent further purification using RP-HPLC, revealing that the F7 fraction offered the best ACE-inhibitory activity. For ACE inhibition, the ideal peptide in the context of the F7 fraction comprised eight amino acids: Phe-Cys-Leu-Tyr-Glu-Leu-Ala-Arg (FCLYELAR), while analysis of the Lineweaver-Burk plot revealed that the FCLYELAR peptide can serve as an uncompetitive ACE inhibitor. An examination of the molecular docking process showed that the FCLYELAR peptide was primarily able to provide ACE-inhibitory qualities as a consequence of the hydrogen bond interactions taking place between ACE and the peptide. Furthermore, upon isolation form the SBPH, the ACE-inhibitory peptide demonstrated ACE-inhibitory capabilities in vitro, underlining its potential for applications in the food and pharmaceutical sectors.

Highlights

One of the major causes of death around the world today is cardiovascular disease (CVD)
Reports have indicated that water molecules which were present had not permeated into the tissue of the bone, but were found only on the surface, so the drying process in an oven would remove almost all of the water
The results of this work demonstrated that salmon bone has a high potential for usage as a material for isolating and characterizing angiotensin I-converting enzyme (ACE)-inhibitory peptides via the trypsin hydrolysis process

Summary

Introduction

One of the major causes of death around the world today is cardiovascular disease (CVD). Blood pressure and balance of fluids will normally be governed by the renin-angiotensin system, which is a hormone system that is highly influential in CVD pathophysiology, especially in the case of congestive heart failure and hypertension. It is the plasma renin which converts angiotensinogen which comes from the liver into angiotensin I; proteolytic cleavage takes place when angiotensin I is exposed to angiotensin I-converting enzyme (ACE), resulting in the formation of angiotensin II in the lungs. These properties explain why ACE inhibitors are likely to have a positive effect on patients with hypertension, and may present further benefits in reducing CVDs [4, 5]

Methods

Results

Conclusion