In Vitro Generation and Stability of the Lactokinin β-Lactoglobulin Fragment (142–148)

Department of Life Sciences, University of Limerick, Ireland.
Journal of Dairy Science (Impact Factor: 2.57). 12/2004; 87(11):3845-57. DOI: 10.3168/jds.S0022-0302(04)73524-9
Source: PubMed


The objectives of this study were to investigate the generation of beta-lactoglobulin fragment (142-148) (beta-LG f(142-148) during the hydrolysis of whey proteins, and the in vitro stability of this fragment upon incubation with gastrointestinal and serum proteinases and peptidases. An enzyme immunoassay (EIA) protocol was developed for the quantification of beta-LG f(142-148) in whey protein hydrolysates and in human blood serum. The minimum detection limit was 3 ng/mL. The level of the peptide in whey protein hydrolysates was influenced by the degree of hydrolysis (DH). As expected, highest levels of this peptide were found in hydrolysates generated with trypsin. Sequential incubation of hydrolysates at different DH values with pepsin and Corolase PP, to simulate gastrointestinal digestion, generally resulted in the degradation of beta-LG f(142-148) as determined by EIA. Reversed-phase HPLC and angiotensin-I-converting enzyme (ACE) activity assays demonstrated that synthetic beta-LG f(142-148) was rapidly degraded upon incubation with human serum. Furthermore, beta-LG f(142-148) could not be detected by EIA in the sera of 2 human volunteers following its oral ingestion or in sera from these volunteers subsequently spiked with beta-LG f(142-148). These in vitro results indicate that beta-LG f(142-148) is probably not sufficiently stable to gastrointestinal and serum proteinases and peptidases to act as an hypotensive agent in humans following oral ingestion. The in vitro methodology described herein has general application in evaluating the hypotensive potential of food protein-derived ACE inhibitory peptides.

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    • "Human blood contains a large number of serum peptidases, which can further hydrolyse the bioactive peptide and reduce activity. For example, the b-lactoglobulin-derived ACE-inhibitory peptide (f142–148; Ala–Leu–Pro–Met– His–Ile–Arg) was shown to be degraded in vitro by gastrointestinal and serum proteinases destroying its potential bioactive properties (Walsh et al. 2004). "
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    • "There are several examples of peptides, which showed potent ACE-inhibitory activity, but did not exert an antihypertensive effect in vivo. For instance, peptide a S1 -casein f(23–27) showed potent ACE-inhibitory activity, but no hypotensive effect in SHR (Maruyama et al., 1987), and peptide b-lactoglobulin f(142–148) with in vitro ACE-inhibitory activity but no effect in human volunteers (Walsh et al., 2004). "
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