5.7 Opioid Peptides
Opioid peptides are short amino acid sequences present in dairy products that play
an active role in the nervous system. These peptides have pharmacological similarity with opium (morphine) and exert their activity by binding to specific
receptors in the target cell. Typical opioid peptides are all originated from precursor
proteins such as endorphins, enkephalins, and dynorphins, and they have the same
N-terminal sequence, Tyr-GlyGly-Phe. Opioid peptides derived from other precursor proteins, such as serum proteins, are called “atypical” [132]. That is, they
consist of several amino acid sequences where only Tyr is conserved in the
N-terminal region. Thus, the N-terminal sequence of “atypical” opioid peptides is
Tyr-X-Phe or Tyr-X-X-Phe. It seems that the presence of Tyr and another aromatic
amino acid form an essential structural motive involved in connection with opioid
receptors. These opioid-like sequences are encrypted in the primary structure of the
main whey proteins, in particular in fragments released from a-LA and b-LG such
as YGLF f(50–53) and YLLF f(102–105), respectively named a- and
b-Lactorphins. Kostyra et al. [132] also identified several atypical” opioid peptides
released from BSA, such as ALKAWSVAR f(208–216) and YGFQNA f(399–404).
The roles played by food-derived opioid peptides in central nervous and gastrointestinal systems were recently reviewed by Liu and Udenigwe [133], while
Garg et al. [134] recently reviewed the opioid peptides released from food proteins.
6 Conclusions and Perspectives
Enzymatic catalysis is an essential strategy for hydrolysis of milk and whey proteins in useful products such as bioactive peptides. The ability of different enzymes
and conditions to generate bioactive peptides were the subject of intensive research
worldwide. Several proteolytic enzymes are used to produce products derived from
whey proteins presenting a wide range of remarkable biological activities, including
antimicrobial, antioxidant, antihypertensive, and antidiabetic activities. The association of this variety of biological activities with several peptide sequences was
reviewed in this chapter. Whey proteins are (and will be) an important source for
the production and discovery of new bioactive peptides.
Proteins and peptides from milk and whey components continue to be preferred
as potential ingredients for functional and nutraceutical foods, and as active
medicinal agents. This preference is based on the strong consumer trend in the
search for health and well-being. The mechanisms of action of bioactive peptides
still need to continue to be fully elucidated.
Future research should focus on new hydrolysis processes of whey proteins
under conditions resembling those used on a large scale. Furthermore, the search of
less common proteases such as proteolytic enzymes from plants and marine
organisms with the potential to release new unique amino acid sequences will
undoubtedly be active fields of research. The high cost of purification and actual
498
A. F. A. Salvado et al.
Opioid peptides are short amino acid sequences present in dairy products that play
an active role in the nervous system. These peptides have pharmacological similarity with opium (morphine) and exert their activity by binding to specific
receptors in the target cell. Typical opioid peptides are all originated from precursor
proteins such as endorphins, enkephalins, and dynorphins, and they have the same
N-terminal sequence, Tyr-GlyGly-Phe. Opioid peptides derived from other precursor proteins, such as serum proteins, are called “atypical” [132]. That is, they
consist of several amino acid sequences where only Tyr is conserved in the
N-terminal region. Thus, the N-terminal sequence of “atypical” opioid peptides is
Tyr-X-Phe or Tyr-X-X-Phe. It seems that the presence of Tyr and another aromatic
amino acid form an essential structural motive involved in connection with opioid
receptors. These opioid-like sequences are encrypted in the primary structure of the
main whey proteins, in particular in fragments released from a-LA and b-LG such
as YGLF f(50–53) and YLLF f(102–105), respectively named a- and
b-Lactorphins. Kostyra et al. [132] also identified several atypical” opioid peptides
released from BSA, such as ALKAWSVAR f(208–216) and YGFQNA f(399–404).
The roles played by food-derived opioid peptides in central nervous and gastrointestinal systems were recently reviewed by Liu and Udenigwe [133], while
Garg et al. [134] recently reviewed the opioid peptides released from food proteins.
6 Conclusions and Perspectives
Enzymatic catalysis is an essential strategy for hydrolysis of milk and whey proteins in useful products such as bioactive peptides. The ability of different enzymes
and conditions to generate bioactive peptides were the subject of intensive research
worldwide. Several proteolytic enzymes are used to produce products derived from
whey proteins presenting a wide range of remarkable biological activities, including
antimicrobial, antioxidant, antihypertensive, and antidiabetic activities. The association of this variety of biological activities with several peptide sequences was
reviewed in this chapter. Whey proteins are (and will be) an important source for
the production and discovery of new bioactive peptides.
Proteins and peptides from milk and whey components continue to be preferred
as potential ingredients for functional and nutraceutical foods, and as active
medicinal agents. This preference is based on the strong consumer trend in the
search for health and well-being. The mechanisms of action of bioactive peptides
still need to continue to be fully elucidated.
Future research should focus on new hydrolysis processes of whey proteins
under conditions resembling those used on a large scale. Furthermore, the search of
less common proteases such as proteolytic enzymes from plants and marine
organisms with the potential to release new unique amino acid sequences will
undoubtedly be active fields of research. The high cost of purification and actual
498
A. F. A. Salvado et al.