Abstract
We examined the inhibitory activity of angiotensin I converting enzyme (ACE) in protein hydrolysates from dulse, Palmaria palmata. The proteins extracted from dulse were mainly composed of phycoerythrin (PE) followed by phycocyanin (PC) and allophycocyanin (APC). The dulse proteins showed slight ACE inhibitory activity, whereas the inhibitory activity was extremely enhanced by thermolysin hydrolysis. The ACE inhibitory activity of hydrolysates was hardly affected by additional pepsin, trypsin and chymotrypsin treatments. Nine ACE inhibitory peptides (YRD, AGGEY, VYRT, VDHY, IKGHY, LKNPG, LDY, LRY, FEQDWAS) were isolated from the hydrolysates by reversed-phase high-performance liquid chromatography (HPLC), and it was demonstrated that the synthetic peptide LRY (IC50: 0.044 μmol) has remarkably high ACE inhibitory activity. Then, we investigated the structural properties of dulse phycobiliproteins to discuss the origin of dulse ACE inhibitory peptides. Each dulse phycobiliprotein possesses α-subunit (Mw: 17,477–17,638) and β-subunit (Mw: 17,455–18,407). The sequences of YRD, AGGEY, VYRT, VDHY, LKNPG and LDY were detected in the primary structure of PE α-subunit, and the LDY also exists in the APC α- and β-subunits. In addition, the LRY sequence was found in the β-subunits of PE, PC and APC. From these results, it was suggested that the dulse ACE inhibitory peptides were derived from phycobiliproteins, especially PE. To make sure the deduction, we carried out additional experiment by using recombinant PE. We expressed the recombinant α- and β-subunits of PE (rPEα and rPEβ, respectively), and then prepared their peptides by thermolysin hydrolysis. As a result, these peptides showed high ACE inhibitory activities (rPEα: 94.4%; rPEβ: 87.0%). Therefore, we concluded that the original proteins of dulse ACE inhibitory peptides were phycobiliproteins.
Highlights
Angiotensin I converting enzyme (ACE: EC 3.4.15.1) is physiologically important in the regulation of blood pressure catalyzing the production of angiotensin II and the destruction of bradykinin [1].Mar
2a, 2a, thethe protein extracts from dulse red colour, which is supposed to originate from PE
The maximum absorption wavelength of dulse proteins was in the range of red colour, which is supposed to originate from PE
Summary
Angiotensin I converting enzyme (ACE: EC 3.4.15.1) is physiologically important in the regulation of blood pressure catalyzing the production of angiotensin II and the destruction of bradykinin [1]. ACE inhibitory peptides found in in enzymatic hydrolysates of many foodstuffs [2,3,4,5,6,7].[2,3,4,5,6,7]. Studied inhibitory peptides brown alga Undaria pinnatifida (wakame) that is that a popular traditional foodstuff in Japanin[8]. They seven ACE inhibitory peptides from from the hydrolysates of U. It was reported reported popular in Ireland and Atlantic Canada as a food and a source the dulse protein hydrolysates show inhibitory effects for renin [12] and dipeptidyl peptidase IV [13].
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