title: Screening for peptides from fish and cheese inhibitory to prolyl endopeptidase.
abstract: Peptides from hydrolysates of fish proteins and from cheeses were analysed for inhibition of prolyl endopeptidase (PE) isolated from porcine muscle. Muscles of cod, salmon, and trout were homogenised and incubated at pH 4.0 with pepsin and then at pH 7.5 with trypsin to obtain fish protein hydrolysates. Homogenates were incubated without exogenous enzymes at pH 4.0 and 7.5 to obtain fish protein autolysates. Water-soluble extracts from "rakfisk" (a Norwegian fermented/autolysed trout muscle dish) and water-soluble extracts from Cheddar, Norvegia, Jarlsberg, and Blue cheese were also prepared. Peptides in the supernatants obtained after heat-treatment of fish hydrolysates, autolysates and water-soluble extracts of rakfisk and cheeses at 95 degrees C for 15 min were analysed for inhibition of PE. Inhibition was also measured in peptide fractions separated by reversed-phase high-performance chromatography and by gel permeation chromatography. The peptide fractions from fish hydrolysates, fish autolysates, and water-soluble extracts of cheeses inhibited PE in hydrolysing Z-Gly-Pro-amidomethylcoumarin. Inhibition by peptides from rakfisk was negligible. Pepsin + trypsin hydrolysates from the three fish species contained PE inhibitory peptides with a broad range of apparent hydrophobicity and apparent molecular mass. Autolysates from muscles of the 3 fish species contained narrow peptide peaks of different molecular mass and different apparent hydrophobicity with strong PE inhibitory activity. The content of hydrophilic inhibitory peptides was lower in cheeses than in pepsin + trypsin hydrolysates of fish muscle.
authors.affiliation: Dept. of Chemistry, Biotechnology and Food Science, Agricult. Univ. of Norway, P.O. Box 5003, N-1432 As, Norway. raymond.sorensen@ikbm.nlh.no
authors.forename: Raymond
authors.initials: R
authors.lastname: Sørensen
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kildal
authors.forename: Leszek
authors.initials: L
authors.lastname: Stepaniak
authors.forename: Are Hugo
authors.initials: AH
authors.lastname: Pripp
authors.forename: Terje
authors.initials: T
authors.lastname: Sørhaug
mesh_terms: D000818:Animals; D002611:Cheese / Q000032:analysis*; D002850:Chromatography, Gel / Q000379:methods; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D005399:Fishes / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D009124:Muscle Proteins / Q000737:chemistry* / Q000502:physiology; D010446:Peptide Fragments / Q000032:analysis* / Q000494:pharmacology / Q000502:physiology; D000085822:Prolyl Oligopeptidases; D012474:Salmon / Q000378:metabolism; D012697:Serine Endopeptidases / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology*; D013552:Swine; D014337:Trout / Q000378:metabolism
chemical_list: D009124:Muscle Proteins; D010446:Peptide Fragments; D015842:Serine Proteinase Inhibitors; D012697:Serine Endopeptidases; D000085822:Prolyl Oligopeptidases