Kunio Suetsuna

Identification of an antihypertensive peptide from peptic digest of wakame (Undaria pinnatifida).

A peptide fraction having activity against angiotensin I-converting enzyme (ACE) was separated from the peptic digest of protein prepared from wakame (Undaria pinnatifida) by ion-exchange chromatographies and gel-filtration. Fractions with high ACE inhibitory activity were combined and further chromatographed on a reverse-phase column to yield four tetrapeptides with ACE inhibitory properties. These tetrapeptides were identified by sequence analysis and fast atom bombardment mass spectrometry as Ala-Ile-Tyr-Lys (IC(50): 213 microM), Tyr-Lys-Tyr-Tyr (64.2 microM), Lys-Phe-Tyr-Gly (90.5 microM), and Tyr-Asn-Lys-Leu (21 microM). Each tetrapeptide was synthesized and its antihypertensive activity was determined after oral administration in spontaneously hypertensive rats. The blood pressure significantly decreased after tetrapeptide ingestion. The present study demonstrated that dietary wakame may have beneficial effects on hypertension.

Isolation and characterization of angiotensin I-converting enzyme inhibitor dipeptides derived from Allium sativum L (garlic)

Abstract A concentrate of an aqueous extract of Allium sativum L. (garlic) was fractionated using ion exchange and gel filtration to isolate fractions with angiotensin I-converting enzyme (ACE) inhibitory activity. Fractions with high ACE inhibitory activity were combined and further chromatographed on a reverse-phase column to yield seven dipeptides with ACE inhibitory properties. These dipeptides were identified by sequence analysis and fast atom bombardment mass spectrometry as Ser-Tyr, Gly-Tyr, Phe-Tyr, Asn-Tyr, Ser-Phe, Gly-Phe, and Asn-Phe, with IC50 (the amount of peptide needed to inhibit ACE activity) values of 66.3, 72.1, 3.74, 32.6, 130.2, 277.9, and 46.3 μM, respectively. Each dipeptide was synthesized and its antihypertensive activity was determined after oral administration in spontaneously hypertensive rats. The blood pressure lowering activity of the dipeptides was lower than that of captopril. However, the presence of these dipeptides in garlic suggests that these compounds may, at least in part, be responsible for the observed antihypertensive effect of garlic (or garlic extracts) in animals and humans. Further, long-term use of dietary garlic may have a protective effect against rise in blood pressure.

Isolation and characterization of immunostimulative peptides from soybean

Immunostimulative peptides were isolated from the pepsin digest of soybean by ion exchange, gel filtration, and reversed-phase high-performance chromatography. The peptides formed blastoids against the splenocytes of CSH/HeN mice. The amino acid sequences of these peptides were: Ala-Glu-lle-Asn-Met-Pro-Asp-Tyr, Ile-Gln-Gln-Gly-Asn, and Ser-Gly-Phe-Ala-Pro, respectively.

Immunological effects of dietary peptide derived from soybean protein

Abstract The effect of dietary peptides derived from soybean and casein on the immune responsiveness of Fisher rats has been investigated. The protein efficiency ratio of these diets was similar. The phagocytosis of opsonized sheep red blood cells by alveolar macrophages (AMo) and the mitogenic activity of rats fed both peptides, particularly soybean peptide, were found to be significantly greater than those of rats fed the corresponding proteins of soybean and casein. Furthermore, in the pair-feeding experiment using both peptides, a comparable enhancement of the phagocytic activity of AMo was seen in the rats given the peptides, but little difference in the natural killer cell activity was noted among rats fed each diet. It was suggested that immune activating factors would be presented in the soybean peptide.