A novel angiotensin I converting enzyme inhibitory peptide from tuna frame protein hydrolysate and its antihypertensive effect in spontaneously hypertensive rats

Tuna frame protein was hydrolysed using Alcalase, Neutrase, pepsin, papain, alpha-chymotrypsin and trypsin. Peptic hydrolysate exhibited the highest ACE I inhibitory activity among them and was fractionated into three ranges of molecular weight (below 1, 1-5 and 5-10 kDa) using an ultrafiltration membrane bioreactor system. The 1-5 kDa fraction showed the highest ACE inhibitory activity and was used for subsequent purification steps. During consecutive purification, a potent ACE inhibitory peptide from tuna frame protein (PTFP), which was composed of 21 amino acids, Gly-Asp-Leu-Gly-Lys-Thr-Thr-Thr-Val-Ser-Asn-Trp-Ser-Pro-Pro-Lys-Try-Lys-Asp-Thr-Pro (MW: 2,482 Da, IC50: 11.28 mu m), was isolated. Lineweaver-Burk plots suggest that PTFP plays as a non-competitive inhibitor against ACE. Furthermore, anti hypertensive effect in spontaneously hypertensive rats (SHR) also revealed that oral administration of PTFP can decrease systolic blood pressure significantly (P < 0.01). These results suggest that the PTFP would be a beneficial ingredient for nutraceuticals and pharmaceuticals against hypertension and its related diseases. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.