Affiliation:
1. Dipartimento di Protezione delle Piante e Microbiologia Applicata, Facoltà di Agraria, Università degli Studi di Bari
2. Dipartimento di Scienze degli Alimenti, Università degli Studi di Perugia, Italy
3. Unité de Biochimie et Structure des Protéines, INRA, 78352 Jouy-en-Josas, France
4. Department of Food and Nutritional Sciences, University College, Cork, Ireland
Abstract
ABSTRACT
Sodium caseinates prepared from bovine, sheep, goat, pig, buffalo or human milk were hydrolyzed by a partially purified proteinase of
Lactobacillus helveticus
PR4. Peptides in each hydrolysate were fractionated by reversed-phase fast-protein liquid chromatography. The fractions which showed the highest angiotensin I-converting-enzyme (ACE)-inhibitory or antibacterial activity were sequenced by mass spectrum and Edman degradation analyses. Various ACE-inhibitory peptides were found in the hydrolysates: the bovine α
S1
-casein (α
S1
-CN) 24-47 fragment (f24-47), f169-193, and β-CN f58-76; ovine α
S1
-CN f1-6 and α
S2
-CN f182-185 and f186-188; caprine β-CN f58-65 and α
S2
-CN f182-187; buffalo β-CN f58-66; and a mixture of three tripeptides originating from human β-CN. A mixture of peptides with a C-terminal sequence, Pro-Gly-Pro, was found in the most active fraction of the pig sodium caseinate hydrolysate. The highest ACE-inhibitory activity of some peptides corresponded to the concentration of the ACE inhibitor (
S
)-
N
-(1-[ethoxycarbonyl]-3-phenylpropyl)-ala-pro maleate (enalapril) of 49.253 μg/ml (100 μmol/liter). Several of the above sequences had features in common with other ACE-inhibitory peptides reported in the literature. The 50% inhibitory concentration (IC
50
) of some of the crude peptide fractions was very low (16 to 100 μg/ml). Some identified peptides were chemically synthesized, and the ACE-inhibitory activity and IC
50
s were confirmed. An antibacterial peptide corresponding to β-CN f184-210 was identified in human sodium caseinate hydrolysate. It showed a very large spectrum of inhibition against gram-positive and -negative bacteria, including species of potential clinical interest, such as
Enterococcus faecium
,
Bacillus megaterium
,
Escherichia coli
,
Listeria innocua
,
Salmonella
spp.,
Yersinia enterocolitica
, and
Staphylococcus aureus
. The MIC for
E. coli
F19 was ca. 50 μg/ml. Once generated, the bioactive peptides were resistant to further degradation by proteinase of
L. helveticus
PR4 or by trypsin and chymotrypsin.
Publisher
American Society for Microbiology
Subject
Ecology,Applied Microbiology and Biotechnology,Food Science,Biotechnology
Cited by
243 articles.
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