Immunologically active peptides that accompany hen egg yolk immunoglobulin Y: separation and identification

Abstract

The protein mixture of cytokine-inducing activity accompanying chicken immunoglobulin Y, named yolkin, consists of several peptides of molecular weight (MW) ranging from over 1 to 35 kDa. Yolkin and its constituent peptides were found to be efficient inducers of interleukin (IL)-1β, IL-6 and IL-10 secretion. N-terminal amino acid sequences of eight of the electrophoretically purified yolkin constituents revealed that all of them are homological to some fragments of the C-terminal domain of vitellogenin II. The fractions of MW about 4 and 12 kDa are free of carbohydrates and start at position 1732 in the vitellogenin amino acid sequence; whereas the other fractions (MW about 16, 19, 23, 29, 32 and 35 kDa) appeared to be glycoproteins corresponding to the amino acid sequence of vitellogenin starting at position 1572. From these data, it is concluded that yolkin most likely represents vitellogenin-derived peptides that possess cytokine-inducing activity and are, at least partially, responsible for such properties of separated immunoglobulin Y preparation. This finding reveals a new role for vitellogenin as a reservoir of polypeptides that may play an important role in the innate immune system of the developing embryo.

Yolkin- A Polypeptide Complex Isolated From Chicken Egg Yolk with Potential Neuroprotective and Antioxidative Activity

“…This may indicate that Vg plays a more general function, regardless of gender, making it a particularly interesting protein [1]. The main egg yolk plasma proteins are accompanied by protein fragments released from the C-terminal region of Vg, such as yolk plasma glycoprotein YPG40 and a 42 kDa proteolytic fragment of the vitellogenin I [1][2][3]. Vitellogenin (Vg) is a phosphoprotein of molecular weight from 250 kDa to 600 kDa present in serum.…”

“…Vg was initially recognized as a female-specific protein, but recently its presence has also been demonstrated in males. This indicates that Vg in much smaller quantities can play an additional yet unknown biological function, making this protein very interesting [1][2][3][4]. Chicken Vg consists of three species, designated as vitellogenins I, II and III [2].…”

“…It has been proven that Vt II is enzymatically hydrolyzed into main proteins belonging to the granule fraction of egg yolk namely: lipovitelein I (fragment of N-terminal region), phosvitin (phosphoserylrich domain of Vg) and lipovitelein II. While protein fragments corresponding to the N-terminal Vg domain are well-known, there is no precise identification of the vitellogenin C-terminal region [1,2].…”

“…Research Agnieszka Zabłocka shown to have a higher cytokine inducing activity than purified IgY, indicating a new biological function of C terminal Vg fragments. Additionally, among the yolkin constituents, peptides with molecular weights of about 20.4 kDa and 23.2 kDa exert the strongest cytokine IL 6 inducing activity [1]. It has also been shown that yolkin modulates nitric oxide release from mouse macrophages, and down-regulates lipid peroxidation [4,5].…”

“…Taken together, the immune-regulatory properties of yolkin indicate it may be a promising bioactive compound to promote neuroprotection and inhibit the progression of dementia in the course of neurodegenerative disorders [1,4]. In this regard, we had previously tested the impact of yolkin on cognitive functions in young and old rats as a model of cognitive decline and the process of brain aging.…”