235
chymotrypsin hydrolyze proteins to oligopeptides in the lumen of small intestine,
(3) oligopeptides further broken down to di-, tri- peptides or single amino acids and
are ready for absorption (Chung et al. 1979). By the use of this method antioxidant
and antihypertensive peptides were generated in past (Lee and Hur 2017; Jamdar
et al. 2017; Li et al. 2007). Vilcacundo et al. (2017) has even reported generation of
antidiabetic peptides during simulated gastrointestinal digestion of quinoa proteins.
Bioactive peptides can also be generated following the ingestion process either
by digestive (gastric and intestinal) enzymes or by microbial enzymes present in the
gastro-intestinal tract. Therefore, the proteins during their passage through the
digestive tract become the target of enzymes, which are normally present in the
gastrointestinal tract. A wide range of enzymes with different specificity may act
throughout the whole gastrointestinal tract and under conditions, which may differ
depending on various physiological factors (Antalis et al. 2007). In this case, the
digestion process is far less easy to control and monitor. Therefore, in vitro simulated gastrointestinal digestion (SGID) is commonly employed to investigate the
stability of milk proteins and check the effect on the stability of bioactive peptides
upon their transit through SGID. SGID takes into account key factors affecting the
digestion process such as the rates of gastric emptying, which are used to determine
the period of incubation with gastric proteases, and changes in gastric pH value
which determine to a large extent the enzyme activity (De Noni 2008).
GI digestion of casein and/or whey proteins by pepsin, trypsin and chymotrypsin
has been reported to released several bioactive peptides (Meisel and FitzGerald
2003; Gobbetti et al. 2002, 2004). The GI digestion requires the generated peptide
to be intact at the time of absorption or action in the intestine. Since most dietary
proteins fully breakdown while passing through the small intestine, it means that the
protein or peptide must be somewhat resistant to proteolysis if an effect is to be
observed (Rutherfurd-Markwick 2012). There are examples of proteins (immunoglobulins and lactoferrin) which showcase this property of partial resistance (Roos
et al. 1995; Drescher et al. 1999; Moller et al. 2008). Similarly, caseins have also
shown to block the active site of proteolytic enzymes thereby shielding certain peptides from digestion (Rutherfurd-Markwick 2012).
Chemical Hydrolysis
This method involves cleavage of peptide bonds with either alkali or acid solutions.
Chemical hydrolysis is not only difficult to control but can be damaging to certain
amino acid groups like serine and threonine (Rutherfurd-Markwick 2012), destroy
protein substrate, and form toxic substances like lysino-alanine (Clemente 2000).
Thus, the limitations of this process have significantly reduced its application in
generating peptides with biological activities.
Bioactive Peptides Derived from Different Sources
chymotrypsin hydrolyze proteins to oligopeptides in the lumen of small intestine,
(3) oligopeptides further broken down to di-, tri- peptides or single amino acids and
are ready for absorption (Chung et al. 1979). By the use of this method antioxidant
and antihypertensive peptides were generated in past (Lee and Hur 2017; Jamdar
et al. 2017; Li et al. 2007). Vilcacundo et al. (2017) has even reported generation of
antidiabetic peptides during simulated gastrointestinal digestion of quinoa proteins.
Bioactive peptides can also be generated following the ingestion process either
by digestive (gastric and intestinal) enzymes or by microbial enzymes present in the
gastro-intestinal tract. Therefore, the proteins during their passage through the
digestive tract become the target of enzymes, which are normally present in the
gastrointestinal tract. A wide range of enzymes with different specificity may act
throughout the whole gastrointestinal tract and under conditions, which may differ
depending on various physiological factors (Antalis et al. 2007). In this case, the
digestion process is far less easy to control and monitor. Therefore, in vitro simulated gastrointestinal digestion (SGID) is commonly employed to investigate the
stability of milk proteins and check the effect on the stability of bioactive peptides
upon their transit through SGID. SGID takes into account key factors affecting the
digestion process such as the rates of gastric emptying, which are used to determine
the period of incubation with gastric proteases, and changes in gastric pH value
which determine to a large extent the enzyme activity (De Noni 2008).
GI digestion of casein and/or whey proteins by pepsin, trypsin and chymotrypsin
has been reported to released several bioactive peptides (Meisel and FitzGerald
2003; Gobbetti et al. 2002, 2004). The GI digestion requires the generated peptide
to be intact at the time of absorption or action in the intestine. Since most dietary
proteins fully breakdown while passing through the small intestine, it means that the
protein or peptide must be somewhat resistant to proteolysis if an effect is to be
observed (Rutherfurd-Markwick 2012). There are examples of proteins (immunoglobulins and lactoferrin) which showcase this property of partial resistance (Roos
et al. 1995; Drescher et al. 1999; Moller et al. 2008). Similarly, caseins have also
shown to block the active site of proteolytic enzymes thereby shielding certain peptides from digestion (Rutherfurd-Markwick 2012).
Chemical Hydrolysis
This method involves cleavage of peptide bonds with either alkali or acid solutions.
Chemical hydrolysis is not only difficult to control but can be damaging to certain
amino acid groups like serine and threonine (Rutherfurd-Markwick 2012), destroy
protein substrate, and form toxic substances like lysino-alanine (Clemente 2000).
Thus, the limitations of this process have significantly reduced its application in
generating peptides with biological activities.
Bioactive Peptides Derived from Different Sources