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PubMed1991

Design of bioactive peptides based on antibody hypervariable region structures. Development of conformationally constrained and dimeric peptides with enhanced affinity.

The variable regions of antibody molecules bind antigens with high affinity and specificity. This binding is imparted largely by the hypervariable portions of the variable region. Hypervariable regions typically fold into reverse turn or loop structures. Peptides derived from antibody hypervariable region sequences can bind antigens with similar specificity, albeit with markedly lower affinity. In this study, cyclic and dimeric peptide analogs of an anti-idiotypic/antireceptor antibody hypervariable region were developed. This antibody (87.92.6) binds to reovirus type 3 receptors on cells as well as to a neutralizing anti-reovirus type 3 monoclonal antibody (9B.G5). The cyclic peptides were utilized to probe the optimal conformation for binding to both the receptor and 9B.G5. By dimerizing or constraining the conformation of these peptides, higher affinity binding was produced. By utilizing several different cyclic peptides, the optimal conformation for binding was established. The conformationally optimized cyclic peptide possessed greater than 40-fold higher affinity for the receptor and the idiotype than the linear analog. This study suggests that conformationally constrained and dimeric peptides derived from antibody hypervariable loop sequences can bind antigens (including receptors) with reasonable affinity. hypervariable loop sequences can bind antigens (including

Amino Acid Sequence↗
PubMed1997

Interaction of cells with UHMWPE impregnated with the bioactive peptides RGD, RGE or Poly-L-lysine.

Several reports have suggested that encapsulation of orthopaedic and dental implants with fibrous tissue can lead to implant failure. The binding of cells to the surface of the implants is specific to amino-acid sequences, typically RGD. The specific objective of this study was to investigate the interaction of cultured human peripheral macrophages with specific amino-acid sequences to determine if adherence is due to the specificity of such sequence. Macrophages were seeded at a density of 1 x 10(5) cells on ultra high molecular weight polyethylene (UHMWPE) coated with either amino-acid heteropolymers of RGE, RGD, or amino-acid homopolymer Poly-L-Lysine. Cells were observed daily and morphology was recorded. The results showed that cells growing in the presence of RGD had significantly (p < 0.05) higher numbers of cells adhering and remaining viable, in comparison to cells growing on Poly-L-lysine or RGE. Cells growing on UHMWPE coated with RGE appeared irregularly (elongated and spindle) shaped and unevenly spaced. The cells growing in the presence of Poly-L-Lysine showed cellular disruption and lysis, whereas cells growing on the RGD appeared intact, regularly spaced and began fusing into giant cells. Lactate dehydrogenase activity was used as a measure of membrane integrity, and cells grown on UHMWPE coated with Poly-L-lysine showed a two-fold increase in activity over control and peptide treated groups. Immunochemical analysis for cytokine (IL-1) release as a measure of cellular reactivity revealed an increase level in the experimental groups after 24 hours and remained measurable over the duration of the experiment. Cells incubated on uncoated polyethylene showed no evidence of increased cytokine response. Overall, the results show macrophages can interact with specific coating on the material surface, and these surfaces can affect the adhesion process adherence. Use of RGE, which inhibits binding of the cells, may be a factor that can be used to coat implants to increase their longevity.

Amino Acid Sequence↗
PubMed2000

Bioactive milk peptides: a prospectus.

Bioactive peptides have been identified within the amino acid sequences of native milk proteins. Hydrolytic reactions, such as those catalyzed by digestive enzymes, result in their release. These peptides directly influence numerous biological processes evoking behavioral, gastrointestinal, hormonal, immunological, neurological, and nutritional responses. The specific bioreactions associated with each physiological class have been well characterized. Herein, we review the scientific literature and attempt to stimulate consideration of the continued use of bioactive peptides and their expanded development as a commercial product. Several applications have already evolved. For example, phosphopeptides derived from casein fractions are currently used as both dietary and pharmaceutical supplements. Potentially, the addition of bioactive peptides to food products could improve consumer safety as a result of their antimicrobial properties. Lastly, bioactive peptides may function as health care products, providing therapeutic value for either treatment of infection or prevention of disease.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2003

Release of angiotensin I converting enzyme (ACE) inhibitory activity during in vitro gastrointestinal digestion: from batch experiment to semicontinuous model.

Gastrointestinal digestion is of major importance in the bioavailability of angiotensin I converting enzyme (ACE) inhibitory peptides, bioactive peptides with possible antihypertensive effects. In this study, the conditions of in vitro gastrointestinal digestion leading to the formation and degradation of ACE inhibitory peptides were investigated for pea and whey protein. In batch experiments, the digestion simulating the physiological conditions sufficed to achieve the highest ACE inhibitory activity, with IC(50) values of 0.076 mg/mL for pea and 0.048 mg/mL for whey protein. The degree of proteolysis did not correlate with the ACE inhibitory activity and was always higher for pea than whey. In a semicontinuous model of gastrointestinal digestion, response surface methodology studied the influence of temperature and incubation time in both the stomach and small intestine phases on the ACE inhibitory activity and degree of proteolysis. For pea protein, a linear model for the degree of proteolysis and a quadratic model for the ACE inhibitory activity could be constituted. Within the model, a maximal degree of proteolysis was observed at the highest temperature and the longest incubation time in the small intestine phase, while maximal ACE inhibitory activity was obtained at the longest incubation times in the stomach and small intestine phase. These results show that ACE inhibitory activity of pea and whey hydrolysates can be controlled by the conditions of in vitro gastrointestinal digestion.

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1999

Bioactivity of peptide analogs of the neutrophil chemoattractant, N-acetyl-proline-glycine-proline.

PURPOSE: The release of N-acetyl-proline-glycine-proline (PGP), a chemoattractant resulting from direct alkaline hydrolysis of corneal proteins, is believed to be the initial trigger for neutrophil invasion into the alkali-injured cornea. The purpose of this study is twofold: (1) to compare the activity of N-acetyl-PGP with the bioactivities of other similar synthetic peptides in an effort to uncover information about this chemoattractant molecule, and (2) to test these peptide analogs as potential antagonists of N-acetyl-PGP. METHODS: The polarization assay was used to measure the potential chemotactic response of human neutrophils to peptides. Bioactivity was expressed as the peptide concentration required to produce 50% neutrophil polarization (EC50). Antagonist activity was expressed as the peptide concentration required to produce 50% inhibition (ID50) of polarization activated by N-acetyl-PGP. RESULTS: Peptide bioactivities (EC50) were ranked as follows: APGPR (0.34 mM) > N-acetyl-PGP (0.5 mM) > N-(PGP)4-PGLG (3 mM) = t-Boc-PGP (3 mM) > N-acetyl-PG (3.4 mM) > N-methyl-PGP (15 mM) = PGP (15 mM) > peptides without detectable activity (t-Boc-PGP-OMe, N-acetyl-P, PG, PGG, GP, GG and gly-pro-hyp). Peptides with no detectable bioactivity were tested as potential antagonists of neutrophil polarization induced by N-acetyl-PGP. Gly-Pro-Hyp inhibited N-acetyl-PGP activation of polarization at 20 mM (ID50). No other synthetic peptide demonstrated a capacity for inhibition. CONCLUSIONS: The minimum requirement to elicit bioactivity was the presence of PGP alone or derivatives of PG in which the N-terminal proline is blocked. Using this approach, active and inactive mimetic peptides of N-acetyl-PGP were produced. The most active peptide, APGPR, was equal to or slightly greater than N-acetyl-PGP, suggesting that more potent analogs might be designed. Gly-pro-hyp was the only inactive peptide analog to inhibit the chemoattractant.

Chemotactic Factors↗
PubMed2003

Cross-linked thermoresponsive anionic polymer-grafted surfaces to separate bioactive basic peptides.

Cross-linked, thermoresponsive poly(N-isopropylacrylamide-co-acrylic acid-co-N-tert-butylacrylamide) [poly(IPAAm-co-AAc-co-tBAAm)] thin hydrogel layers on silica beads were used as new column matrix modifiers for LC separation of basic bioactive peptides, angiotensin subtypes I, II, and III. Terpolymer poly(IPAAm-co-AAc-co-tBAAm) showed both phase transition and apparent carboxylate pKa shifts in water, depending on temperature. Polymer-grafted silica bead surfaces exhibited simultaneous thermally modulated changes in hydrophilic/hydrophobic properties and charge densities. More effective separation of angiotensin peptide subtypes was achieved on columns of these terpolymer thin hydrogel grafted surfaces, as compared to an uncharged control binary copolymer of IPAAm and tBAAm. Although hydrophobic interactions effect separation of angiotensin subtypes, combined electrostatic and hydrophobic interaction resulted in more pronounced retention. At temperature below the terpolymer phase transition, hydrophobic interactions predominated, and minimal changes in electrostatic interactions were supported by little shift in the apparent AAc carboxylate pKa values. Above the phase transition temperature, electrostatic interactions were dramatically reduced as a result of the decreased charge densities of the polymer grafted surfaces. Therefore, peptide retention times were also reduced, exhibiting a maximum at near 30-35 degrees C. Interestingly, column retention behavior of angiotensins is dramatically modulated by applied step temperature gradients. Thermoresponsive surface property alteration is a very rapid, reversible phenomenon, allowing step temperature gradients on thermoresponsive columns to enable the analogous performance advantages as gradient elution in reversed-phase HPLC. More importantly, injected peptides were recovered completely from the columns from calculation of peak area. In conclusion, these anionic thermoresponsive polymer-modified surfaces are good candidates for improved separation of bioactive peptides under exclusively aqueous conditions.

Amino Acid Sequence↗
PubMed1990

Immunocytochemical evidence of vertebrate bioactive peptide-like molecules in the immuno cell types of the freshwater snail Planorbarius corneus (L.) (Gastropoda, Pulmonata).

An immunocytochemical investigation was carried out on round and spreading hemocytes of Planorbarius corneus by using 20 antisera to vertebrate bioactive peptides. The immunotests showed the presence of alpha 1-antichymotrypsin-bombesin-, calcitonin-, CCK-8 (INC)-, CCK-39-, gastrin-, glucagon-, Met-enkephalin-, neurotensin-, oxytocin-, somatostatin-, substance P-, VIP-, and vasopressin-immunoreactive molecules in the spreading hemocytes. The round hemocytes were only positive to anti-bombesin, anticalcitonin, anti-CCK-8 (INC), anti-CCK-39, anti-neurotensin, anti-oxytocin, anti-substance P and anti-vasopressin antibodies. No immunostaining was observed with anti-CCK-8 (Peninsula), anti-insulin, anti-prolactin, anti-thyroglobulin and anti-thyroxin (T4) antibodies. As probably in vertebrates, these bioactive peptides may modulate immuno cell function.

Animals↗
PubMed1999

Proposing sequences for peptides derived from whey fermentation with potential bioactive sites.

In fed-batch fermentation by Kluyveromyces marxianus var. marxianus, whey-soluble proteins were converted into oligopeptides. To assess whether bioactive peptides could be produced during whey fermentation, K. marxianus was cultured in batch in deproteinized media containing 5 or 15% (wt/vol) dehydrated whey for 20 h and then was in fed-batch mode for 50 h. After harvesting the biomass (25,000 x g, 15 min), at 6-h intervals, the wort was analyzed to determine protein consumption and oligopeptide production by HPLC. The proteins in the wort showed an oscillatory degradation with a constant increase in the production of oligopeptides. Four major peaks were collected and were analyzed by API mass spectroscopy. Sequences of fermented peptides were compared with sequences of known bioactive peptides. On the basis of their molecular weights, two amino acid sequences were proposed. The presence of sites containing the peptide sequence of beta-lactorphin (YLLF) suggests that these oligopeptides may have antihypertensive properties.

Amino Acid Sequence↗
PubMed2004

Multifunctional peptides encrypted in milk proteins.

Many bioactivities of milk are latent in that they are inactive within the protein sequence, requiring enzymatic proteolysis for release of bioactive peptides from milk proteins precursors. Bioactivities of peptides encrypted in major milk proteins are latent until released and activated, e.g. during gastrointestinal digestion or food processing. Bioactive peptides can be produced in vivo following intake of milk proteins, and the proteolytic system of bacterial species used in the production of fermented milk products and cheese can contribute to the liberation of bioactive peptides or precursors thereof. Activated peptides are potential modulators of various regulatory processes in the living system: immunomodulatory peptides stimulate the activities of cells of the immune system and several cytomodulatory peptides inhibit cancer cell growth, antimicrobial peptides kill sensitive microorganisms, angiotensin-I-converting enzyme (ACE)-inhibitory peptides exert an hypotensive effect, opioid peptides are opioid receptor ligands which can modulate absorption processes in the intestinal tract, mineral binding peptides may function as carriers for different minerals, especially calcium. Many milk-derived peptides reveal multifunctional properties, i.e. specific peptide sequences having two or more different biological activities have been reported. Milk protein-derived bioactive peptides are claimed to be health enhancing components that can be used to reduce the risk of disease or to enhance a certain physiological function.

Animals↗
PubMed1995

Localization of a domain in apolipoprotein E with both cytostatic and cytotoxic activity.

Apoliprotein E (apoE) is a potent suppressor of interleukin 2- (IL2-) dependent T lymphocyte proliferation. In this study, we have used a range of monomeric and dimeric peptides encompassing amino acids 130-169 in human apoE to locate a region with both cytostatic and cytotoxic effects on IL2-dependent T lymphocytes. Monomeric peptides representing residues 130-149 or 130-155 inhibited the proliferation of the cells without causing loss of cell viability. However, cytostasis by a peptide representing the extended 130-169 domain or dimeric peptides of amino acids 141-155 or 141-149 was accompanied by potent cytotoxic activity. These results suggest that residues 141-149, which include the overlap between the functional peptides, are responsible for cytostasis and cytotoxicity. Complete ablation of both activities by the polyanionic agent heparin highlighted the important contribution of the positively charged amino acids in the 141-149 region to peptide bioactivity. Furthermore, the bioactive apoE peptides also had a relatively high helical content, suggesting that alpha-helical content is necessary for bioactivity. Cytotoxic apoE peptides were characterized by a high density of polar face positively charged residues together with a high nonpolar face hydrophobicity. This conclusion is supported by the reduced hydrophobicity and polar face positive charge density of the significantly less active E2(130-169) peptide. The cytotoxic apoE peptides are structurally similar to previously characterized class L lytic peptides. They do not, however, exert their cytotoxic activity by destabilizing membrane bilayers as is the case with the class L peptides, as evidenced by their minimal hemolytic activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed2004

Attachment of hyaluronan to metallic surfaces.

Metal implants are in general not compatible with the tissues of the human body, and in particular, blood exhibits a severe hemostatic response. Herein we present results of a technique to mask the surface of metals with a natural biopolymer, hyaluronan (HA). HA has minimal adverse interactions with blood and other tissues, but attachment of bioactive peptides can promote specific biological interactions. In this study, stainless steel was cleaned and then surface-modified by covalent attachment of an epoxy silane. The epoxy was subsequently converted to an aldehyde functional group and reacted with hyaluronan through an adipic dihydrazide linkage, thus covalently immobilizing the HA onto the steel surface. Fluorescent labeling of the HA showed that the surface had a fairly uniform covering of HA. When human platelet rich plasma was placed on the HA-coated surface, there was no observable adhesion of platelets. HA derivatized with a peptide containing the RGD peptide sequence was also bound to the stainless steel. The RGD-containing peptide was bioactive as exemplified by the attachment and spreading of platelets on this surface. Furthermore, when the RGD peptide was replaced with the nonsense RDG sequence, minimal adhesion of platelets was observed. This type of controlled biological activity on a metal surface has potential for modulating cell growth and cellular interactions with metallic implants, such as vascular stents, orthopedic implants, heart valve cages, and more.

Amino Acid Sequence↗
PubMed2004

Immunostimulatory role of tryptic digest of Abrus agglutinin.

Many bioactive peptides are in therapeutic use as immunomodulators at present. The origin of these bioactive peptides is diverse. Such bioactive peptides are reported to be present in enzymatic digest of food and milk proteins. In our previous work we have reported that Abrus agglutinin retains its bioactivity even after heat denaturation but loses its haemagglutination properties. This leads to the supposition that immunostimulatory regions in the protein might be responsible for its in vivo and in vitro stimulatory properties. Thus the bioactivity of tryptic digest of Abrus agglutinin (TDA) was checked in vitro to ascertain the presence of some bioactive region in the protein, which will lead to the discovery of certain immunostimulatory peptides which might be of use in nonspecific immunotherapy. In this study it is observed that TDA stimulates macrophage increasing the phagocytic and bactericidal activity as well as hydrogen peroxide production. TDA also proliferates splenocytes leading to Th1 response and NK cell activation.

Adjuvants, Immunologic↗
PubMed1989

Purification and substrate specificity of a strongly hydrophobic extracellular metalloendopeptidase ("gelatinase") from Streptococcus faecalis (strain 0G1-10).

An extracellular Zn-endopeptidase was purified to homogeneity from the culture filtrates of Streptococcus faecalis (human oral strain 0G1-10) by a procedure that comprised concentration in an Amicon Hollow Fiber System, ammonium sulfate precipitation, gel permeation chromatography, hydrophobic interaction chromatography (batch operation on phenyl-sepharose Cl-4B), followed by fast protein liquid chromatography (FPLC) on a phenyl-Superose HR 5/5 column, and finally FPLC on a Superose 12 HR 10/30 column. The enzyme is a 31.5-kDa strongly hydrophobic protein with an isoelectric point of 4.6 and a broad pH optimum of 6 to 8. The substrate specificity of the enzyme is similar to that of the mammalian membrane endopeptidase-24.11 and Streptococcus thermophilus thermolysin (EC 3.4.24.4) in hydrolyzing preferentially the Phe24-Phe25 bond in insulin B-chain, followed by cleavage of the His5-Leu6 bond. The enzyme was especially active on Azocoll and gelatin; soluble and insoluble collagens were hydrolyzed at a lower rate. S. faecalis sex pheromone-related peptides and several mammalian bioactive peptides were cleaved at sites involving pronounced hydrophobicity. The enzyme did not hydrolyze small synthetic peptide derivatives (phenylazobenzyloxycarbonyl-L-Pro-L-Leu-Gly-L-Pro-D-Arg and 2-furylacryloyl-L-Leu-Gly-L-Ala) that are typically attacked by "true" bacterial collagenases. Chemical modification indicated the importance of histidyl, carboxyl, and tyrosyl groups in enzyme activity, suggesting that this enzyme may thus be classified as a metalloprotease II (EC 3.4.24.4). The enzyme is strongly inhibited by a 720-kDa factor present in rat inflammatory exudate. The pronounced ability of the enzyme to attack collagenous materials and certain bioactive peptides suggests its participation in inflammatory processes involving the presence of S. faecalis.

Amino Acids↗