No 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.

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A member of the Ascaris inhibitor family exhibiting anti-cathepsin G and anti-chymotrypsin activity was purified from the larval hemolymph of the honey bee (Apis mellifera). Three forms of the inhibitor, designated AMCI 1±3, were isolated using gel filtration and anion-exchange chromatographies followed by reverse-phase HPLC. The amino-acid analyses indicated that AMCI-1 and AMCI-2 have an identical composition whereas AMCI-3 is shorter by two residues (Thr, Arg). All three forms contain as many as 10 cysteine residues and lack tryptophan, tyrosine, and histidine. The sequence of the isoinhibitors showed that the major form (AMCI-1) consisting of 56 amino-acid residues was a single-chain protein of molecular mass 5972 Da, whereas the other two forms were two-chain proteins with a very high residue identity. The AMCI-2 appeared to be derived from AMCI-1, as a result of the Lys24-Thr25 peptide bond splitting, while AMCI-3 was truncated at its N-terminus by the dipeptide Thr25-Arg26. The association constants for the binding of bovine a-chymotrypsin to all purified forms of the inhibitor were high and nearly identical, ranging from 4.8 Â 10 10 m 21 for AMCI-1 to 2.7 Â 10 9 m 21 for AMCI-3. The sensitivity of cathepsin G to inhibition by each inhibitor was different. Only the association constant for the interaction of this enzyme with AMCI-1 was high (2 Â 10 8 m 21) whereas those for AMCI-2 and AMCI-3 were significantly lower, and appeared to be 3.7 Â 10 7 m 21 and 4.5 Â 10 6 m 21 , respectively. The reactive site of the inhibitor, as identified by cathepsin G degradation and chemical modification, was found to be at Met30-Gln31. A search in the Protein Sequence Swiss-Prot databank revealed a significant degree of identity (44%) between the primary structure of AMCI and the trypsin isoinhibitor from Ascaris sp (ATI) .On the basis of the cysteine residues alignment, the position of the reactive site as well as some sequence homology, the cathepsin G/chymotrypsin inhibitor from larval hemolymph of the honey bee may be considered to be a member of the Ascaris inhibitor family.

Numerous studies have shown that food proteins may be a source of bioactive peptides. Those peptides are encrypted in the protein sequence. They stay inactive within the parental protein until release by proteolytic enzymes (Mine and Kovacs-Nolan in Worlds Poult Sci J 62(1):87–95, 2006; Hartman and Miesel in Curr Opin Biotechnol 18:163–169, 2007). Once released the bioactive peptides exhibit several biofunctionalities and may serve therapeutic roles in body systems. Opioid peptides, peptides lowering high blood pressure, inhibiting platelet aggregation as well as being carriers of metal ions and peptides with immunostimulatory, antimicrobial and antioxidant activities have been described (Hartman and Miesel in Curr Opin Biotechnol 18:163–169, 2007). The biofunctional abilities of the peptides have therefore aroused a lot of scientific, technological and consumer interest with respect to the role of dietary proteins in controlling and influencing health (Möller et al. in Eur J Nutr 47(4):171–182, 2008). Biopeptides may find wide application in food production, the cosmetics industry as well as in the prevention and treatment of various medical conditions. They are manufactured by chemical and biotechnological methods (Marx in Chem Eng News 83(11):17–24. 2005; Hancock and Sahl in Nat Biotechnol 24(12):1551–1557, 2006). Depending on specific needs (food or pharmaceutical industry) different degrees of peptide purifications are required. This paper discusses the practicability of manufacturing bioactive peptides, especially from food proteins.