Plant-Derived Proteins and Peptides as Potential Immunomodulators

The immune response of humans may be modulated by certain biopeptides. The present study aimed to determine the immunomodulatory potential of plant-derived food proteins and hydrolysates obtained from these proteins via monocatalytic in silico hydrolysis (using ficin, stem bromelainm or pepsin (pH > 2)). The scope of this study included determinations of the profiles of select bioactivities of proteins before and after hydrolysis and computations of the frequency of occurrence of selected bioactive fragments in proteins (parameter A), frequency/relative frequency of the release of biopeptides (parameters A_E, W) and the theoretical degree of hydrolysis (DH_t), by means of the resources and programs available in the BIOPEP-UWM database. The immunomodulating (ImmD)/immunostimulating (ImmS) peptides deposited in the database were characterized as well (ProtParam tool). Among the analyzed proteins of cereals and legumes, the best precursors of ImmD immunopeptides (YG, YGG, GLF, TPRK) turned out to be rice and garden pea proteins, whereas the best precursors of ImmS peptides appeared to be buckwheat (GVM, GFL, EAE) and broad bean (LLY, EAE) proteins. The highest number of YG sequences was released by stem bromelain upon the simulated hydrolysis of rice proteins (AE = 0.0010-0.0820, W = 0.1994-1.0000, DH_t = 45-82%). However, antibacterial peptides (IAK) were released by ficin only from rice, oat, and garden pea proteins (DH_t = 41-46%). Biopeptides (YG, IAK) identified in protein hydrolysates are potential immunomodulators, nutraceuticals, and components of functional food that may modulate the activity of the human immune system. Stem bromelain and ficin are also active components that are primed to release peptide immunomodulators from plant-derived food proteins.