title: Identification of ACE-inhibitory peptides in salt-free soy sauce that are transportable across caco-2 cell monolayers.
abstract: In present study, we aimed to identify angiotensin I-converting enzyme (ACE)-inhibitory peptides from a salt-free soy sauce (SFS), a newly developed antihypertensive seasoning obtained by Aspergillus oryzae fermentation of soybean in the absence of salt, which can be transported through caco-2 cell monolayers. Through an Ussing transport investigation of SFS across caco-2 cell monolayers, three di-peptides, Ala-Phe, Phe-Ile and Ile-Phe, were successfully identified from the SFS as transportable inhibitory peptides. Ala-Phe and Ile-Phe, but not Phe-Ile, exhibited ACE-inhibitory activity with IC(50) values of 165.3 microM and 65.8 microM, respectively. Kinetic studies revealed that Ile-Phe (Km: 3.1 mM, P(app): 2.4 x 10(-6) cm/s) exhibited greater affinity toward the transport compared with Ala-Phe (K(m): 48.1 mM, P(app): 1.4 x 10(-6) cm/s) and Phe-Ile (K(m): 12.7 mM, P(app): 1.4 x 10(-6) cm/s).
authors.affiliation: Division of Bioscience and Bioenvironmental Sciences, Faculty of Agriculture, Graduate School of Kyushu University, Fukuoka, Japan.
authors.forename: Xiao-Lin
authors.initials: XL
authors.lastname: Zhu
authors.forename: Keisuke
authors.initials: K
authors.lastname: Watanabe
authors.forename: Koso
authors.initials: K
authors.lastname: Shiraishi
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Ueki
authors.forename: Yoshiharu
authors.initials: Y
authors.lastname: Noda
authors.forename: Toshiro
authors.initials: T
authors.lastname: Matsui
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Matsumoto
mesh_terms: D000806:Angiotensin-Converting Enzyme Inhibitors / Q000302:isolation & purification / Q000493:pharmacokinetics*; D001692:Biological Transport; D018938:Caco-2 Cells; D002462:Cell Membrane / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007700:Kinetics; D010455:Peptides / Q000302:isolation & purification / Q000493:pharmacokinetics*; D012492:Salts; D045730:Soy Foods / Q000032:analysis*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D010455:Peptides; D012492:Salts