Ex vivo digestion of carp muscle tissue--ACE inhibitory and antioxidant activities of the obtained hydrolysates.

In the digestive tract of humans, bioactive peptides, i.e. protein fragments impacting the physiological activity of the body, may be released during the digestion of food proteins, including those of fish. The aim of the study was to establish the method of human ex vivo digestion of carp muscle tissue and evaluate the angiotensin I-converting enzyme inhibitory and antioxidant activities of hydrolysates obtained after digestion. It was found that the hydrolysates of carp muscle tissue obtained with the three-stage method of simulated ex vivo digestion showed ACE inhibitory as well as antioxidative activities. It was demonstrated that the degree of hydrolysis depended on the duration of individual stages and the degree of comminution of the examined material. Although the applied gastric juices initiated the process of hydrolysis of carp muscle tissue, the duodenal juices caused a rapid increase in the amount of hydrolysed polypeptide bonds. The antihypertensive and antioxidative activities of the hydrolysates of carp muscle tissue increased together with progressive protein degradation. However, the high degree of protein hydrolysis does not favour an increase in the activity of free radical scavenging. The presented results are an example of the first preliminary screening of the potential health-promoting biological activity of carp muscle tissue in an ex vivo study.

Database of biologically active peptide sequences.

Proteins are sources of many peptides with diverse biological activity. Such peptides are considered as valuable components of foods with desired and designed biological activity. Two strategies are currently recommended for research in the area of biological activity of food protein fragments. The first strategy covers investigations on products of enzymic hydrolysis of proteins. The second one is synthesis of peptides identical with protein fragments and investigations using these peptides. It is possible to predict biological activity of protein fragments using sequence alignments between proteins and biologically active peptides from database. Our database contains currently 527 sequences of bioactive peptides with antihypertensive, opioid, immunomodulating and other activities. The sequence alignments can give information about localization of biologically active fragments in protein chain, but not about possibilities of enzymic release of such fragments. The information is thus equivalent with this obtained using synthetic peptides identical with protein fragments. Possibilities offered by the database are discussed using wheat alpha/beta-gliadin, bovine beta-lactoglobulin and bovine beta-casein (including influence of genetic polymorphism and genetic engineering on amino acid sequences) as examples.