Isolation of a heptapeptide Val-Val-Tyr-Pro-Trp-Thr-Gln (valorphin) with some opiate activity

Side-Selective Solid-Phase Metallaphotoredox N(in)-Arylation of Peptides

Postsynthetic diversification of peptides through selective modification of endogenous amino acid side chains has enabled significant advances in peptide drug discovery while expanding the biological and medical chemistry space. However, current tools have been focused on the modification of reactive polar and ionizable side chains, whereas the decoration of aromatic systems (e.g., the N(in) of the tryptophan) has been a long-standing challenge. Here, we introduce metallaphotocatalysis in solid-phase peptide synthesis for the on-resin orthogonal N-arylation of relevant tryptophan-containing peptides. The protocol allows the chemoselective introduction of a new C(sp2)-N bond at the N(in) of tryptophan in biologically active protected peptide sequences in the presence of native redox-sensitive side chains. The fusion of metallaphotocatalysis with solid-phase peptide synthesis opens new perspectives in diversifying native amino acid side chains.

Behavioral Effects and Analgesic Profile of Hemoglobin-Derived Valorphin and Its Synthetic Analog in Rodents

Valorphin (V1) is a naturally occurring peptide derived from hemoglobin that has been found to have an affinity for opioid receptors and exhibits antinociceptive and anticonvulsant activity. Some of its synthetic analogs containing an aminophosphonate moiety show structure-dependent potent antinociceptive effects. This study aimed to reveal a detailed picture of the antinociceptive mechanisms and behavioral effects of V1 and its recently synthesized phosphopeptide analog V2p in rodents using a range of methods. The studied peptides significantly reduced acute (mean V1-9.0, V2p-5.8 vs. controls-54.1 s) and inflammatory (mean V1-57.9 and V2p-53.3 vs. controls-107.6 s) nociceptive pain in the formalin test, as well as carrageenan-induced hyperalgesia (mean V1-184.7 and V2p-107.3 vs. controls-61.8 g) in the paw pressure test. These effects are mediated by activation of opioid receptors with a predominance of kappa in V1 antinociception and by delta, kappa, and mu receptors in V2p-induced antinociception. Both peptides did not change the levels of TNF-alpha and IL-1-beta in blood serum. V1 induces depression-like behavior, and V2p shows a tendency toward anxiolysis and short-term impairment of motor coordination without affecting exploratory behavior. The results characterize valorphin and its derivative as promising analgesics that exert their effects both centrally and peripherally, without causing severe behavioral changes in experimental animals. These encouraging data are a foundation for future studies focusing on the effects of hemorphins after long-term treatment.

Interaction of hemorphins with ACE homologs

Hemorphins, short bioactive peptides produced by enzymatic cleavage of β-hemoglobin, exhibit antihypertensive properties by inhibiting angiotensin-1 converting enzyme (ACE1). ACE1 is a key player in the renin-angiotensin system (RAS) and regulates blood pressure. ACE1 and its homolog, ACE2, which exhibit opposing activities in the RAS, share considerable similarity in their catalytic domains. The primary objective of this study was to identify and contrast the molecular mechanisms underlying the interaction of hemorphins of camels and that of other mammals with the two ACE homologs. In silico docking and molecular dynamics simulations were performed for ACE1 and ACE2, along with in vitro confirmatory assays for ACE1. The C-domain of ACE1, primarily involved in regulating blood pressure, was used along with the N-terminal peptidase domain of ACE2. The findings revealed conserved hemorphin interactions with equivalent regions of the two ACE homologs and differential residue-level interactions reflecting the substrate preferences of ACE1 and ACE2 considering their opposing functions. Therefore, conserved residue-level associations and implications of poorly conserved regions between the two ACE receptors may potentially guide the discovery of selective domain-specific inhibitors. The findings of this study can provide a basis for the treatment of related disorders in the future.

Synthesis and characterization of new 5,5′-dimethyl- and 5,5′-diphenylhydantoin-conjugated hemorphin derivatives designed as potential anticonvulsant agents

Herein, the synthesis and characterization of some novel N-modified hybrid analogues of hemorphins containing a C-5 substituted hydantoin residue as potential anticonvulsants and for the blockade of sodium channels are presented.

Antinociceptive Effects of VV-Hemorphin-5 Peptide Analogues Containing Amino phosphonate Moiety in Mouse Formalin Model of Pain

BACKGROUND

Hemorphins are endogenous hemoglobin-derived peptides that belong to the family of "atypical" opioid peptides with both affinities to opioid receptors and ability to release other endogenous opioid peptides.

OBJECTIVE

In the present study, peptide analogues of Valorphin (VV-hemorphin-5) containing amino phosphonate moiety synthesized by solid-phase peptide synthesis (Fmoc-strategy) were investigated for their potential antinociceptive activities and compared to the reference VV-H in formalin- induced model of acute and inflammatory pain in mice.

METHODS

The hemorphin analogues were prepared by replacement of the one and/or two N-terminal Val in VV-hemorphin5 (VV-H) with ((dimethoxy phosphoryl) methyl)-L-valine and ((dimethoxy phosphoryl) methyl)-L-leucine to obtain the compounds pVV-H, pL-H, and pLV-H. Aiming to additionally prove the importance of amino acid valine, we introduced the ((dimethoxy phosphoryl) methyl)-L-leucine to the N-side of VV-hemorphin-5 (pLVV-H). The experiments were carried out on adult male ICR mice. All peptides were administered intracerebroventricularly at three doses (50, 25 and 12,5 μg/mouse). We have studied the effects of the peptides on acute (1st phase) and inflammatory (2nd phase) pain reaction using un experimental model with intraplantar formalin injection.

RESULTS

VV-H showed a significant antinociceptive effect both in the acute and inflammatory phases of the test. Although Valorphin hexa-, hepta-, and octapeptide analogs demonstrated a significant antinociceptive effect, they showed substantial differences considering their effective dose and the phase of the test as compared to the Valorphin.

DISCUSSION

Data showed that modified heptapeptides pVV-H and pLV-H exerted the same or better antinociception in acute and inflammatory pain, in comparison to the reference peptide, while pL-H and pLVV-H analogues were less effective.

CONCLUSION

Our study contributes to the elucidation of the role of Valine and the number of amino acid residues in the structure of hemorphin peptide analogs in their effectiveness in suppressing both acute and inflammatory experimental pain.

Structure-activity relationship study on new hemorphin-4 analogues containing steric restricted amino acids moiety for evaluation of their anticonvulsant activity

In the present study, several new analogues of hemorphin-4, modified with unnatural conformationally restricted amino acids followed the structure Aaa-Tyr-Xxx-Trp-Thr-NH₂, where Aaa is the low-molecular-weight lipophilic adamantyl building block, and Xxx is Ac5c (1-aminocyclopentanecarboxylic acid) or Ac6c (1-aminocyclohexane carboxylic acid) was synthesized, characterized and investigated for anticonvulsant activity in three seizure tests, the maximal electroshock test (MES), 6-Hz psychomotor seizure test and timed intravenous pentylenetetrazole infusion (ivPTZ) test. The acute neurological toxicity was determined using the rota-rod test. The new synthetic neuropeptide analogues were prepared by solid-phase peptide synthesis-Fmoc chemistry and were evaluated in three doses of 1, 3 and 5 µg, respectively, administered intracerebroventricularly in male ICR mice. The physicochemical properties of these peptide analogues were evaluated as pKa and pI values were calculated using potentiometry. The IR spectrum of the compounds was recorded and the characteristic lines of both adamantane moiety and the peptide backbone were registered in the wavelength range from 4000 to 400 cm^-1. The hexapeptide Ang IV was used as a positive control. From the six synthesized peptide analogues, the P4-5 was the most active at doses of 1 and 3 µg in the three seizure tests. The order of potency of other peptides was as follows: P4 > P4-3 = P4-4 > P4-2 > Ang IV in MES, P4-4 ≥ P4-1 > P4-3 > P4-2 > P4 > Ang IV in 6-Hz test and P4-4 = P4-3 > P4-2 = P4 > Ang IV in ivPTZ test. None of the peptides displayed neurotoxicity in the rota-rod test. Docking study results suggest that direct H-bonding and ionic interactions between our synthetic ligands and residues, responsible for coordination of Zn²⁺ along with hydrophobic interactions between our ligands and IRAP active site are the most important for the ligand binding. The results propose that incorporation of adamantane and cycloalkane building blocks in the peptide chain of the hemorphin-4 scaffold is important for the potential high biological activity.

Molecular basis of the therapeutic properties of hemorphins

Hemorphins are endogenous peptides, 4-10 amino acids long, belonging to the family of atypical opioid peptides released during the sequential cleavage of hemoglobin protein. Hemorphins have been shown to exhibit diverse therapeutic effects in both human and animal models. However, the precise cellular and molecular mechanisms involved in such effects remain elusive. In this review, we summarize and propose potential mechanisms based on studies that investigated the biological activity of hemorphins of different lengths on multiple therapeutic targets. Special emphasis is given to molecular events related to renin-angiotensin system (RAS), opioid receptors and insulin-regulated aminopeptidase receptor (IRAP). This review provides a comprehensive coverage of the molecular mechanisms that underpin the therapeutic potential of hemorphins. Furthermore, it highlights the role of various hemorphin residues in pathological conditions, which could be explored further for therapeutic purposes.

Potential anticonvulsant activity of novel VV-hemorphin-7 analogues containing unnatural amino acids: synthesis and characterization

Herein, some new analogues of VV-hemorphin-7, modified at position 4 and 7 by the unnatural amino acids followed the structure Val-Val-Tyr-Xxx-Trp-Thr-Yyy-Arg-Phe-NH₂, where Xxx is Ac5c (1-aminocyclopentanecarboxylic acid) or Ac6c (1-aminocyclohexane carboxylic acid) and Yyy is Dap (diaminopropanoic acid) or Dab (diaminobutanoic acid), were synthesized, characterized and investigated for anticonvulsant activity. The new synthetic peptide analogues were prepared by standard solid-phase peptide synthesis-Fmoc chemistry. A single intracerebroventricular (i.c.v.) injection at doses of 5, 10, and 20 µg/10 µl, respectively, was given before evaluation with timed intravenous pentylenetetrazole (ivPTZ) infusion test and 6-Hz psychomotor seizure test in mice. The acute neurological toxicity was determined using the rotarod test. To explain the structure-active properties of the modified peptides, some physicochemical characteristic was obtained. The FT-IR spectra and their second derivatives of the amide I, II, and III bands of the peptides show ß-sheet structure conformation. The calculation of isoelectric points, by potentiometric determination of dissociated constants, is in the range from 9.79 to 10.84. This study, for the first time, also reported on the reduction-oxidative potentials of the guanidine at Arg-moiety on such kind of peptides containing arginine and tyrosine residues in different medium and electrode surface. The VV-hemorphin-7 analogues 4 and 5 were the most active against the ivPTZ test, with the effect comparable to that of peptide 1 used as a positive control. Except compound 8, all other tested peptide analogues were ineffective to raise the threshold for the clonic seizures. The peptide analogue 5 showed 100% protection in the 6-Hz test, while the other seven VV-hemorphin-7 analogues have dose-dependent activity against psychomotor seizures comparable to 1. The novel peptides did not show neurotoxicity in the rotarod test.

Hemoglobin-derived peptides and mood regulation

Evidence accumulated over the past decades has revealed that red blood cells and hemoglobin (Hb) in the blood play important roles in modulating moods and emotions. The number of red blood cells affects the mood. Hb is the principal content in the red blood cells besides water. Denatured Hb is hydrolyzed to produce bioactive peptides. RVD-hemopressin α (RVD-Hpα), which is a fragment of α-chain (95-103) in Hb, functions as a negative allosteric modulator of cannabinoid receptor 1 and a positive allosteric modulator of cannabinoid receptor 2. Hemorphins, which are fragments of β-chain in Hb, exert their effects on opioid receptors. Two hemorphins, namely, LVV-hemorphin-6 and LVV-hemorphin-7, could induce anxiolytic-like effects. The use of Hb-derived bioactive peptides for the treatment of mood disorders is desirable due to cannabinoid-opioid cross modulation and the critical roles of the two systems in physiological processes, such as memory, mood and emotion.

Hemoglobin Reassembly of Antimicrobial Fragments from the Midgut of Triatoma infestans

Hemoglobin is one of the most important molecules of the human body. Beyond its physiological activity, hemoglobins are able to inhibit the growth of several microorganisms. Since 1999, studies have reported that antimicrobial peptides can be produced by blood-feeding insects through hemoglobin digestion, and it has been reported that Triatoma infestans can generate an antimicrobial fragment from human fibrinopeptide. Thus T. infestans intestinal content was analyzed through Reverse Phase High-Performance Liquid Chromatography (RP-HPLC), the eluted fractions were tested against Micrococcus luteus, Escherichia coli and Staphylococcus aureus, and the active fractions submitted to mass spectrometry. The data obtained were compared to hemoglobin databases to verify the presence of hemoglobin-derived fragments. Ten fractions eluted from chromatography presented antimicrobial activity, and when analyzed through mass spectrometry revealed the presence of 8 murine hemoglobin α-chain fragments and 24 fragments from murine hemoglobin β fragments. Through the compilation of the fragments is possible to obtain over 67% coverage of both sequences. Part of the amino acid sequences corresponds to the sequences already identified on other intestinal contents of arthropods, and are highly conserved between the blood of other wild animals that are the most common intermediate hosts of Chagas’ disease in Brazil and some of the main natural blood source for triatomines.

Positive Modulation of Angiotensin II Type 1 Receptor-Mediated Signaling by LVV-Hemorphin-7

Hemorphins are hemoglobin β-chain–derived peptides initially known for their analgesic effects via binding to the opioid receptors belonging to the family of G protein–coupled receptor (GPCR), as well as their physiological action on blood pressure. However, their molecular mechanisms in the regulation of blood pressure are not fully understood. Studies have reported an antihypertensive action via the inhibition of the angiotensin-converting enzyme, a key enzyme in the renin–angiotensin system. In this study, we hypothesized that hemorphins may also target angiotensin II (AngII) type 1 receptor (AT1R) as a key GPCR in the renin–angiotensin system. To investigate this, we examined the effects of LVV–hemorphin-7 on AT1R transiently expressed in human embryonic kidney (HEK293) cells using bioluminescence resonance energy transfer (BRET) technology for the assessment of AT1R/Gαq coupling and β-arrestin 2 recruitment. Interestingly, while LVV–hemorphin-7 alone had no significant effect on BRET signals between AT1R and Gαq or β-arrestin 2, it nicely potentiated AngII-induced BRET signals and significantly increased AngII potency. The BRET data were also correlated with AT1R downstream signaling with LVV–hemorphin-7 potentiating the canonical AngII-mediated Gq-dependent inositol phosphate pathway as well as the activation of the extracellular signal–regulated kinases (ERK1/2). Both AngII and LVV–hemorphin-7–mediated responses were fully abolished by AT1R antagonist demonstrating the targeting of the active conformation of AT1R. Our data report for the first time the targeting and the positive modulation of AT1R signaling by hemorphins, which may explain their role in the physiology and pathophysiology of both vascular and renal systems. This finding further consolidates the pharmacological targeting of GPCRs by hemorphins as previously shown for the opioid receptors in analgesia opening a new era for investigating the role of hemorphins in physiology and pathophysiology via the targeting of GPCR pharmacology and signaling.

Molecular insights into the interaction of hemorphin and its targets

Hemorphins are atypical endogenous opioid peptides produced by the cleavage of hemoglobin beta chain. Several studies have reported the therapeutic potential of hemorphin in memory enhancement, blood regulation, and analgesia. However, the mode of interaction of hemorphin with its target remains largely elusive. The decapeptide LVV-hemorphin-7 is the most stable form of hemorphin. It binds with high affinity to mu-opioid receptors (MOR), angiotensin-converting enzyme (ACE) and insulin-regulated aminopeptidase (IRAP). In this study, computational methods were used extensively to elucidate the most likely binding pose of mammalian LVV-hemorphin-7 with the aforementioned proteins and to calculate the binding affinity. Additionally, alignment of mammalian hemorphin sequences showed that the hemorphin sequence of the camel harbors a variation - a Q > R substitution at position 8. This study also investigated the binding affinity and the interaction mechanism of camel LVV-hemorphin-7 with these proteins. To gain a better understanding of the dynamics of the molecular interactions between the selected targets and hemorphin peptides, 100 ns molecular dynamics simulations of the best-ranked poses were performed. Simulations highlighted major interactions between the peptides and key residues in the binding site of the proteins. Interestingly, camel hemorphin had a higher binding affinity and showed more interactions with all three proteins when compared to the canonical mammalian LVV-hemorphin-7. Thus, camel LVV-hemorphin-7 could be explored as a potent therapeutic agent for memory loss, hypertension, and analgesia.

Synthesis, characterization and anticonvulsant activity of new series of N-modified analogues of VV-hemorphin-5 with aminophosphonate moiety

A new series of N-modified analogues of the VV-hemorphin-5 with aminophosphonate moiety have been synthesized, characterized and investigated for anticonvulsant activity. The novel peptide analogues were prepared by solid-phase peptide synthesis-Fmoc-strategy and were evaluated in the timed intravenous pentylenetetrazole infusion test (ivPTZ) and 6-Hz psychomotor seizure test in mice. The acute neurological toxicity was determined using the rotarod test. The redox potentials at glass carbonic electrode (GC) and the acid/base properties as pKa values of these peptide analogues were compared with the electrochemical behaviour of tyrosine- and tryptophan-containing peptides using different voltamperometric modes. Among the five tested peptide analogues, V3p was the most active against the ivPTZ test with effect comparable to that of the VV-hemorphin-5 (V1) used as a positive control. Dose-dependent elevation of the seizure threshold for myoclonic twitch and generalized clonic seizures was observed after i.c.v. administration of V2p, V4p and V5p as well as for forelimbs tonus in V4p peptides. The peptide analogues V2p-V5p were able to suppress dose-dependent psychomotor seizures in the 6-Hz test. In contrast, the V6p peptide showed either a pro-convulsant effect in the iv PTZ test or was inactive in the 6-Hz test. No changes in motor coordination were noted with the novel peptides. Docking study results suggest that kappa opioid receptor binding could be the mechanism of action of peptide derivatives with anticonvulsant activity. The results suggest that incorporation of aminophosphonate moiety at position 1 of the VV-hemorphin-5 scaffold deserve further evaluation in models of epilepsy and derivatization.

Anticonvulsant evaluation and docking analysis of VV-Hemorphin-5 analogues

VV-Hemorphin-5 is an endogenous opioid peptide of the Hemorphin family with affinity at opioid receptors. A series of C-amide analogues have been synthesized, based on the structure of VV-Hemorphin-5, modified at position 1 and 7 by the un/natural amino acids (Aa8-Val-Val-Tyr-Pro-Trp-Thr-Gln-NH₂ and Val-Val-Tyr-Pro-Trp-Thr-Aa1-NH₂ ) using SPPS, Fmoc-chemistry. The peptide derivatives were evaluated for their anticonvulsant activity in three acute seizure tests in male ICR mice, the maximal electroshock (MES), the 6 Hz psychomotor seizure test, and the timed intravenous pentylenetetrazole (ivPTZ) infusion test. Their neurotoxicity was assessed in the rotarod test. Among the tested peptide analogues, V4 showed anticonvulsant activity in the three seizure tests that was comparable to the VV-Hemorphin-5 (V1) used as a positive control. While V5, V6, and V7 peptide derivatives exhibited anticonvulsant activity in the MES and 6 Hz test, they were inactive (V7) or showed pro-convulsant effect (V5 and V6) in the i.v. PTZ test. At a dose of 10 μg/mouse the peptide V2 was effective against clonic seizures induced by PTZ. Motor coordination was not affected by newly developed analogues of VV-Hemorphin-5. Docking study results suggest that kappa opioid receptor binding could be the mechanism of action of peptide derivatives with anticonvulsant activity. The results suggest that incorporation of nonproteinogenic and/or natural amino acids at position 1 and 7 of the VV-Hemorphin-5 scaffold deserve further evaluation in models of epilepsy and derivatization.

AGH is a new hemoglobin alpha-chain fragment with antinociceptive activity

Limited proteolysis of certain proteins leads to the release of endogenous bioactive peptides. Hemoglobin-derived peptides such as hemorphins and hemopressins are examples of intracellular protein-derived peptides that have antinociceptive effects by modulating G-protein coupled receptors activities. In the present study, a previously characterized substrate capture assay that uses a catalytically inactive form of the thimet oligopeptidase was combined with isotopic labeling and mass spectrometry in order to identify new bioactive peptides. Indeed, we have identified the peptide AGHLDDLPGALSAL (AGH), a fragment of the hemoglobin alpha-chain, which specifically bind to the inactive thimet oligopeptidase in the substrate capture assay. Previous peptidomics studies have identified the AGH as well as many other natural peptides derived from hemoglobin alpha-chain containing this sequence, further suggesting that AGH is a natural endogenous peptide. Pharmacological assays suggest that AGH inhibits peripheral inflammatory hyperalgesic responses through indirect activation of mu opioid receptors, without having a central nervous system activity. Therefore, we have successfully used the substrate capture assay to identify a new endogenous bioactive peptide derived from hemoglobin alpha-chain.

Hemopressin and other bioactive peptides from cytosolic proteins: are these non-classical neuropeptides?

Peptides perform many roles in cell-cell signaling; examples include neuropeptides, hormones, and growth factors. Although the vast majority of known neuropeptides are produced in the secretory pathway, a number of bioactive peptides are derived from cytosolic proteins. For example, the hemopressins are a family of peptides derived from alpha and beta hemoglobin which bind to the CB1 cannabinoid receptor, functioning as agonists or antagonists/inverse agonists depending on the size of the peptide. However, the finding that peptides derived from cytosolic proteins can affect receptors does not prove that these peptides are true endogenous signaling molecules. In order for the hemopressins and other peptides derived from cytosolic proteins to be considered neuropeptide-like signaling molecules, they must be synthesized in brain, they must be secreted in levels sufficient to produce effects, and either their synthesis or secretion should be regulated. If these criteria are met, we propose the name "non-classical neuropeptide" for this category of cytosolic bioactive peptide. This would be analogous to the non-classical neurotransmitters, such as nitric oxide and anandamide, which are not stored in secretory vesicles and released upon stimulation but are synthesized upon stimulation and constitutively released. We review some examples of cytosolic peptides from various protein precursors, describe potential mechanisms of their biosynthesis and secretion, and discuss the possibility that these peptides are signaling molecules in the brain, focusing on the criteria that these peptides would have to fill in order to be considered non-classical neuropeptides.

Bovine hemoglobin: an attractive source of antibacterial peptides

A peptic hemoglobin hydrolysate was fractioned by a semi-preparative reversed-phase HPLC and some fractions have an antibacterial activity against four bacteria strains: Micrococcus luteus A270, Listeria innocua, Escherichia coli and Salmonella enteritidis. These fractions were analyzed by ESI/MS and ESI/MS/MS, in order to characterize the peptides in these fractions. Each fraction contains at least three peptides and some fractions contain five peptides. All these fractions were purified several times by HPLC to obtain pure peptides. Thirty antibacterial peptides were identified. From the isolated antibacterial peptides, 24 peptides were derived from the alpha chains of hemoglobin and 6 peptides were derived from the beta chains of hemoglobin. The lowest concentration of these peptides (minimum inhibitory concentration (MIC)) necessary to completely inhibit the growth of four bacteria strain was determined. The cell population of all of the tested bacteria species decreased by at least 97% after a 24-h incubation with any of the peptides at the minimum inhibitory concentration.

Antinociceptive action of hemopressin in experimental hyperalgesia

Endogenous hemorphins, derived from degradation of the beta-chain of hemoglobin, lower arterial blood pressure and exert an antinociceptive action in experimental models of nociception. Hemopressin, derived from the alpha-chain of hemoglobin, also decreases blood pressure, but its effects on pain have not been studied. In this work, we examined the influence of hemopressin on inflammatory pain. Hemopressin reverted the hyperalgesia induced by either carrageenin or bradykinin when injected concomitantly or 2.5 h after the phlogistic agents. Hemopressin administered systemically also reverted the hyperalgesia induced by carrageenin. Naloxone did not prevent the antinociceptive action of this peptide. These data suggest that hemopressin inhibits peripheral hyperalgesic responses by mechanisms independent of opioid receptor activation.

Hemorphins: substrates and/or inhibitors of dipeptidyl peptidase IV

Hemorphins are endogenous peptides belonging to the family of "atypical" opioid peptides released from sequentially hydrolyzed hemoglobin. In this paper, we report an inhibitory effect of these peptides on dipeptidyl peptidase IV (DPPIV) activity, known to be involved in regulatory functions such as the activation or inactivation of peptides. The structure activity research revealed that hemorphins N-terminus sequence influences nature of the interaction between hemorphins and DPPIV. Kinetic studies conducted with purified DPPIV demonstrated that hemorphin-7 (H7) constitutes a good substrate (K(cat)/K(m) of 137 mM(-1) s(-1)) for this enzyme but could also act as a selective competitive inhibitor by substrate binding site competition. These blood-derived peptides could represent endogenous regulators of this enzyme activity.

In vitro metabolism of LVV-Hemorphin-7 by renal cytosol and purified prolyl endopeptidase

The metabolism of LVVH7, an endogenous peptide obtained by cathepsin D hydrolysis of the beta chain of hemoglobin, was studied, in vitro, in the presence of cytosol of rat kidney and compared with angiotensin IV. High metabolic activity was found against these two peptides (half life time < 2 min) in this subcellular fraction. The main products of LVVH7 metabolism by renal cytosol are VVH7, H7 and LVVH6 suggesting both aminopeptidase and carboxypeptidase activities. The use of PEP inhibitor in kidney cytosol permitted to demonstrate the major role of prolyl endopeptidase (PEP) in LVVH7 degradation. This fact was reinforced by a kinetic study investigated with purified enzyme (Km/Vmax about 238 mM-1 s-1 and close to that observed for angiotensin related peptides).

Family of hemorphins: co-relations between amino acid sequences and effects in cell cultures

Hemorphins, i.e. endogenous fragments of beta-globin chain segment (32-41) LVVYPWTQRY(F) suppress the growth of transformed murine fibroblasts L929 cell culture, the effect is due to cytotoxicity and inhibition of cell proliferation. The contribution of cytotoxicity depends on the presence of Leu(32): VV-hemorphins, except VV-hemorphin-4, exhibit cytotoxicity significantly higher than respective LVV-hemorphins. Decrease of cell number induced by hemorphins depend on the extent of N- and C-terminal degradation of hemorphins: VV-hemorphins in most cases are more active than LVV-, V-hemorphins, and hemorphins. In the group of VV-hemorphins the activity of VV-hemorphin-5 (valorphin) is significantly higher than of VV-hemorphin-7, VV-hemorphin-6, and VV-hemorphin-4, meaning that the presence of C-terminal Gln is important for suppressing of cell number. The amino acid sequence VVYPWTQ corresponding to valorphin was identified as important for manifestation of the both cytotoxic and antiproliferative effects.

Radioligand binding properties of VV-hemorphin 7, an atypical opioid peptide

Receptor binding properties of the hemoglobin-derived nonapeptide VV-hemorphin 7 (Val-Val-Tyr-Pro-Trp-Thr-Gln-Arg-Phe-OH) were studied using both the unlabelled form and tritium-labelled derivative of the peptide. In binding studies using selective opioid radioligands, VV-hemorphin 7 exhibited a rank order of potency of mu > kappa >> delta. VV-hemorphin 7 was tritiated resulting in a compound with 1.03 TBq/mmol (27.8 Ci/mmol) specific radioactivity. The maximal number of binding sites was found to be 66.5 pmol/mg protein with an affinity of 82.1 nM in rat brain membranes. In competition studies, marked similarity was observed to the binding profile of the naturally occurring opioid heptapeptide Met-enkephalin-Arg-Phe (MERF) and its analogues to their naloxone-insensitive binding site. The common -Arg-Phe sequence at the carboxyl terminal end, which is similar to those of other endogenous peptides (-Arg-Phe-NH(2) in neuropeptide FF and FMRF-NH(2)) brings attention to the C-terminal end of the molecule and points to the possible existence of a common nonopioid binding site in mammals.

Complete inhibition of purinoceptor agonist-induced nociception by spinorphin, but not by morphine

We found that spinorphin, a novel neuropeptide showed analgesia in a different manner compared with morphine. By measuring flexor responses induced by the intraplanter injection of substances, the presence of three different types of sensory neurons were demonstrated. Although spinorphin completely blocked 2-metylthioadenosine (2-MeS ATP, a P2X(3) agonist)-induced responses, morphine did not. On the other hand, morphine-induced blockade of bradykinin (BK, a B(2)-receptor agonist)-responses was attenuated by pertussis toxin (PTX) treatment, whereas that of spinorphin was not. Thus it is suggested that spinorphin has a spectrum of analgesia which covers the blockade of nociception insensitive to morphine.

Assessment of stereoselectivity of trimethylphenylalanine analogues of delta-opioid [D-Pen(2),D-Pen(5)]-enkephalin

[D-Pen(2),D-Pen(5)]-Enkephalin (DPDPE) is an enzymatically stable delta-opioid receptor-selective peptide, which was modified by the trimethylation of the Phe(4) residue to give beta-methyl-2', 6'-dimethylphenylalanine (TMP), resulting in four conformations : (2R,3S)-beta-Phe-DPDPE, (2R,3R)-beta-Phe-DPDPE, (2R, 3S)-beta-Phe-DPDPE, and (2S,3R)-beta-Phe-DPDPE. Synthesis was by solid-phase techniques using enantiomerically pure amino acids to give the four optically pure diastereoisomer peptides. The potency and selectivity (delta- versus mu-opioid receptor) were evaluated by radioreceptor binding in rat brain, with a mu/delta ratio decrease for all TMP conformations, compared with the parent compound (DPDPE). Octanol/buffer distribution analysis showed enhanced lipophilicity of all TMP forms, with a sixfold enhancement associated with (2S,3S)-TMP. In situ vascular perfusion in anesthetized rats showed a 1.6-fold (p < 0.01) increase in the ratio of brain uptake for (2S,3S)-TMP and a 1.5-fold (p < 0.01) decrease in uptake for (2R,3R)-TMP. Saturability of (2S,3S)-TMP was shown (p < 0.01) against 100 microM unlabeled DPDPE, showing a shared nondiffusionary transport system. P-glycoprotein affinity was shown in situ for the parent and (2S,3S)-TMP (p < 0.01). Protein binding capacity of the TMP compounds in rat plasma and in situ mammalian bovine serum albumin-Ringer showed (2R,3S)-TMP and (2S,3R)-TMP with the lowest degree of protein binding (p < 0.01), and (2S,3S)-TMP and (2R,3R)-TMP with comparable affinities to DPDPE. Analgesia, via intravenous administration, showed significantly reduced (p < 0.01) end effect and time course for (2R,3R)-TMP, (2R,3S)-TMP, and (2S, 3R)-TMP as compared with DPDPE. These results demonstrate that topographical modification in a conformationally restricted peptide can significantly modulate potency and receptor selectivity, binding capacity, enzymatic stability, lipophilicity, P-glycoprotein affinity, and blood-brain barrier permeability, resulting in a change of bioavailability, and thereby provides insight for future peptide drug design.

Opioid peptides derived from hemoglobin: hemorphins

Investigation of hemoglobin peptic hydrolysate has revealed the presence of biologically active peptides with affinity for opioid receptors. Two peptides, VV-hemorphin-7 and LVV-hemorphin-7, were resolved by a combination of size exclusion and reversed phase HPLC. A new spectroscopic method based on the second order derivative spectra analysis of aromatic amino acids has been developed. This method allows qualitative and quantitative evaluation of hemorphins generated by peptic hemoglobin hydrolysis. Using this method, a kinetic study of hemorphins appearance has been undertaken. In this paper, we also evidenced the generation of VV-hemorphin-7 from globin by peritoneal macrophages. In regard to this result, the putative physiological role of hemorphins is discussed.

The hemorphins: a new class of opioid peptides derived from the blood protein hemoglobin

Hemorphins are endogenous peptides belonging to the family of "nonclassical" or "atypical" opioid peptides. They are generated by enzymatic hydrolysis of the beta-, kappa-, delta-, or epsilon-chain of the blood protein hemoglobin. Originally, the hemorphins were isolated from enzymatically treated bovine blood. In recent years hemorphin structures have been identified as naturally occurring peptides in brain, plasma, and cerebrospinal fluid. This article will review recent studies of the hemorphins regarding their structures, mechanisms for their release, and their biological actions. A particular emphasis will be directed to their role in exercising human and their clinical relevance.

Profiling of endogenous peptides as a tool for studying development and neurological disease

The use of a method to follow changes in endogenous peptide production, as they occur in biological studies, is an excellent complement to other molecular techniques. It has the unique ability to characterize peptides that have been produced from protein precursors, and instrumentation is available that provides high resolution peptide separations that are quantitative, sensitive, and amenable to automation. All tissues express a large number of peptide species that can be visualized, or profiled, on chromatographic separations using reverse-phase high-performance liquid chromatography. This large number of peptides offers many potential molecules that can be used to identify biological mechanisms associated with experimental paradigms. Peptide analysis has been used successfully in many types of studies. In this review, we outline our experience in using peptides as biological markers and provide a description of the evolution of peptide profiling in our laboratories. Peptide expression has been used in studies ranging from how brain regions develop to identifying changes in disease processes including Alzheimer's disease and models of stroke. Some of the findings provided by these studies have been new pathways of peptide processing and the identification of accelerated proteolysis on proteins such as hemoglobin as a function of Alzheimer's disease and brain insult. Peptide profiling has also proven to be an excellent technique for studying many well-known nervous system proteins including calmodulin, PEP-19, myelin basic protein, cytoskeletal proteins, and others. It is the purpose of this review to describe our experience using the technique and to highlight improvements that have added to the power of the approach. Peptide analysis and the expansion in the instrumentation that can detect peptides will no doubt make these types of studies a powerful addition to our molecular armamentarium for conducting biological studies.

Hemoglobin as a source of endogenous bioactive peptides: the concept of tissue-specific peptide pool

Scattered literature data on biologically active hemoglobin-derived peptides are collected in the form of tables. Respective structure-functional correlations are analyzed and the general conclusion is reached that hemoglobin fragments must have a profound physiological function. Evidence is presented that generation of hemoglobin fragments starts inside the erythrocytes. At that stage alpha- and beta-globin chains of hemoglobin predominantly give rise to relatively long peptides containing ca. 30 amino acid residues. The primary proteolysis is followed by the next degradation step coupled with excretion of newly formed shorter peptides form red blood cells. Both the primary and the secondary proteolysis products are subjected to further stepwise C- and N-terminal chain shortening, giving rise to families of closely related peptides that are actually found in animal tissue extracts. The possible sites of primary proteolysis are compared with the positions of the exposed secondary structure elements within the monomeric alpha- and beta-globins as well as the tetrameric hemoglobin. Two tentative schemes are proposed for hemoglobin degradation, one of which starts at the globin loops exposed on the surface of the tetramer and the other, at monomeric globins where more sites are available for the action of proteases. The concept of a "tissue-specific peptide pool" is formulated, describing a novel system of peptidergic regulation, complementary to the conventional hormonal and neuromodulatory systems. According to that description, hemoglobin is only a single example, although an important one, of a vast number of functional proteins providing their proteolytically derived fragments for maintaining the tissue homeostasis.

Bone marrow immunoregulatory peptides (myelopeptides): isolation, structure, and functional activity

Myelopeptides (MPs) are bioregulatory mediators of bone marrow origin. Several individual MPs have been isolated from the supernatant of porcine bone marrow cell culture by successive solid phase extraction and reversed-phase high performance liquid chromatography. Two of them, MP-1 (Phe-Leu-Gly-Phe-Pro-Thr) and MP-2 (Leu-Val-Val-Tyr-Pro-Trp), were synthesized and their biological activities were comprehensively studied. Both hexapeptides display pronounced immunoregulatory activity but their final effects as well as mechanisms of action are different. Peptides MP-1 and MP-2 are identical to conservative fragments 33-38 alpha- and 31-36 beta-chains of hemoglobin, respectively. The sequences of other isolated MPs have no homology with any functional protein. The role of MPs in bioregulatory processes in vivo is discussed.

Bioavailability of Ziconotide in brain: influx from blood, stability, and diffusion

Ziconotide is a selective peptide antagonist of the N-type calcium channel currently in clinical trials for analgesia. Ziconotide reached a maximal brain concentration of between 0.003 and 0.006% of the injected material per gram of tissue at 3-20 min after i.v. injection, and this decayed to below 0.001%/g after 2 h. The structurally distinct conopeptide SNX-185 (synthetic TVIA) was considerably more persistent in brain after i.v. administration, with 0.0035% of the injected material present at 2-4 h after i.v. injection, and 0.0015% present at 24 h. Similar results (i.e. greater persistence of SNX-185) were obtained when the peptides were perfused through in vivo dialysis probes implanted into the hippocampus. Image analysis and serial sectioning showed that diffusion of Ziconotide in the extracellular fluid around the dialysis probe was minimal, with the peptide located within 1 mm of the probe after 2 h. In vitro diffusion through cultured bovine brain microvessel endothelial cells (BBMEC) verified that a close structural analog of Ziconotide (SNX-194) passed through this blood-brain barrier (BBB) model as expected for peptides of similar physical properties (permeability coefficient of 6.5 x 10(-4) cm/g). Passage from blood to brain was also verified by in situ perfusion through the carotid artery. A statistically greater amount of radioactivity was found to cross the BBB after perfusion of radioiodinated Ziconotide compared to [14C]inulin. Capillary depletion experiments and HPLC analysis defined the brain location and stability.

Kinetics of appearance of hemorphins from bovine hemoglobin peptic hydrolysates by a direct coupling of reversed-phase high-performance liquid chromatography and electrospray ionization mass spectrometry

Reversed-phase high-performance liquid chromatography coupled with electrospray ionization mass spectrometry was used to improve the preparation of three opioid peptides (Leu-Val-Val-hemorphin-7, Val-Val-hemorphin-7 and Val-Val-hemorphin-4) resulting from bovine hemoglobin peptic hydrolysates. Optimal conditions for the preparation of these peptides were determined thanks to their kinetic studies of appearance in the course of peptic hydrolyses as a function of degree of hydrolysis of hemoglobin. We propose a low degree of hydrolysis (3%) to prepare Leu-Val-Val-hemorphin-7, a mean degree of hydrolysis (11%) to prepare Val-Val-hemorphin-7 and a high degree of hydrolysis (21%) to prepare Val-Val-hemorphin-4.

Isolation of the opioid peptide Leu-Val-Val-hemorphin-7 from bronchoalveolar lavage fluid of a patient with non-small cell lung cancer

The decapeptide Leu-Val-Val-Tyr-Pro-Trp-Thr-Gln-Arg-Phe was isolated in high yield (1.5 nmol/ml) from bronchoalveolar lavage (BAL) fluid from a patient with an adenocarcinoma of the lung. This peptide, termed LVV-hemorphin-7 represents residues 32-41 of the beta-chain of hemoglobin and has been shown to be an endogenous ligand for opioid receptors. The N-terminal flanking peptide of LVV-hemorphin-7 [residues (1-31) of hemoglobin beta-chain] was also isolated in high yield. Neither peptide was detected in BAL fluid from the tumor-free lung of the same patient or from patients with non-neoplastic inflammatory lung disease. LVV-hemorphin-7 was not identified in BAL fluid from seven additional patients with non-small cell lung cancer, indicating that the formation of the peptide is unlikely to be of any diagnostic significance. However, the ability of LVV-hemorphin-7 to inhibit angiotensin-converting enzyme suggests that its formation may be of pathophysiological significance in the regulation of tumor blood flow in certain patients.

Transport of opioid peptides into the central nervous system

Peptide hormones and neurotransmitters play crucial roles in the maintenance of physiological function at both the cellular and organ level. Although peptide neuropharmaceuticals have enormous potential in the treatment of disease states, the blood-brain barrier (BBB) generally prevents the entry of peptides into the brain either by enzyme degradation or by specific properties of the BBB. Peptides that act at opioid receptors are currently being designed for analgesia and to reduce the unwanted side effects associated with morphine, such as addiction and inhibition of gastric motility. It has been the focus of our group to produce stabile peptide analogues of Met-enkephalin, that lead to analgesia without side effects. In this paper we present the methodologies that have been used to elucidate the transport mechanisms of three peptides across the BBB. Using a primary endothelial cell culture model of the BBB, in situ perfusion, and kinetic analysis we show that D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2 (CTAP) crosses the BBB via diffusion, [D-penicillamine2,5]enkephalin uses a combination of diffusion and a saturable transport mechanism, and biphalin ([Tyr-D-Ala-Gly-Phe-NH]2) uses diffusion and the large neutral amino acid carrier. Understanding BBB transport mechanisms for peptides will aid in the rational design of peptides targeted to the brain.

Cathepsin D is a good candidate for the specific release of a stable hemorphin from hemoglobin in vivo: VV-hemorphin-7

Hemorphin peptides, issued from hemoglobin, are emerging as endogenous bioactive peptides derived from in vivo tissular degradation of hemoglobin. In order to find the enzymes which could be implicated in the in vivo release of these peptides, the major lysosomal enzyme cathepsin D was selected, and a study of its activity towards hemoglobin and hemorphins was performed. In this paper, it is shown that according to the primary specificity of cathepsin D towards hemoglobin, this enzyme could constitute a good candidate for the in vivo release of two hemorphins: LVV-hemorphin-7 and VV-hemorphin-7. Moreover, these products, especially VV-hemorphin-7, are resistant to an extended cleavage by the enzyme. Although LVV-hemorphin-7 exhibits a lower resistance, an extended incubation with cathepsin D led to the release of the stable peptide VV-hemorphin-7.

LVV- and VV-hemorphins: comparative levels in rat tissues

Screening of hemorphins in extracts of rat lung, brain, heart and spleen was carried out. The threshold for detection of hemorphins was 0.01 nmol for spleen and 0.05 nmol for other tissues. Both the content and the composition of hemorphins differed significantly in the tissues analyzed. Heart and lung extracts were rich in these peptides, the content of the most abundant components reaching 16-44 nmol/g of tissue. In contrast, spleen and brain contained much lower amounts of hemorphins, i.e. about 0.3-2.6 nmol/g of tissue. The most represented hemorphin in lung, heart and brain was VV-hemorphin-5, while the content of other members of the hemorphin family depended significantly on the tissue analyzed: lung extract was also rich in LVV-hemorphin-5, heart contained similar amounts of LVV-hemorphin-7 and LVV-hemorphin-5 and brain of LVV-hemorphin-6. In contrast, the hemorphin family in spleen was represented mainly by C-terminally shortened VV-hemorphins, i.e. VV-hemorphin-4 and VV-hemorphin-3. The levels of hemorphins in all cases were sufficient to activate the opioid receptors of the respective tissues.

Peptides from bovine brain: structure and biological role

Fractionation of bovine brain extracts followed by automatic Edman sequencing of individual components resulted in identification of 107 endogenous peptides formed from functional proteins (haemoglobin, myelin basic protein, cytochrome c oxidase, etc) or unknown precursors. Several of the newly identified brain peptides demonstrate different types of biological activity; some of the substances show considerable overlap with the known biologically active peptides. It is suggested that these peptides should participate in regulation of extracellular and intracellular biochemical processes. A concept of 'tissue-specific peptide pool' is formulated describing a novel system of peptidergic regulation, complementary to the conventional hormonal and neuromodulatory systems. According to that description functional proteins provide their proteolytically derived fragments for maintaining the tissue homeostasis by modulating the availability of peptide receptors to respective 'true' ligands.

Modeling of in vivo proteolytic degradation of hemoglobin

Based on the amino acid sequences of endogenous peptides and X-ray spatial structure, mechanism of the in vivo proteolly degradation of bovine hemoglobin was analysed. The degradation was shown to be a multi-stage process. Its first stage is determined by the spatial organization of the native protein substrate, and the next stages-by the distribution of the electrostatic field potential of the protein fragments formed at the earlier stage.

A potent and selective endogenous agonist for the mu-opiate receptor

Peptides have been identified in mammalian brain that are considered to be endogenous agonists for the delta (enkephalins) and kappa (dynorphins) opiate receptors, but none has been found to have any preference for the mu receptor. Because morphine and other compounds that are clinically useful and open to abuse act primarily at the mu receptor, it could be important to identify endogenous peptides specific for this site. Here we report the discovery and isolation from brain of such a peptide, endomorphin-1 (Tyr-Pro-Trp-Phe-NH2), which has a high affinity (Ki = 360 pM) and selectivity (4,000- and 15,000-fold preference over the delta and kappa receptors) for the mu receptor. This peptide is more effective than the mu-selective analogue DAMGO in vitro and it produces potent and prolonged analgesia in mice. A second peptide, endomorphin-2 (Tyr-Pro-Phe-Phe-NH2), which differs by one amino acid, was also isolated. The new peptides have the highest specificity and affinity for the mu receptor of any endogenous substance so far described and they may be natural ligands for this receptor.

Hemorphin peptides are released from hemoglobin by cathepsin D. radioimmunoassay against the C-part of V-V-hemorphin-7: an alternative assay for the cathepsin D activity

In order to investigate the putative physiological role of the in vivo release of hemorphins from hemoglobin in tissues, an immunological approach was developed. Specific and sensitive antiserum were raised against the C-part of the V-V-hemorphin-7. The antisera recognized to the same extent the related hemorphins V-V-hemorphin-7 and L-V-V-hemorphin-7. The validity of our immunological approach was analyzed by studying the in vitro release of hemorphin from hemoglobin by cathepsin D and compared to the pepsin hydrolysis. These two enzymes led to the release of these same products suggesting that cathepsin D acted as an accurate pepsin-like enzyme. Moreover, considering the poor sensitivity of the available methods of detection for the in vitro Cathepsin D activity, our specific and sensitive V-V-hemorphin-7 radioimmunoassay seems to be a useful alternative assay for this enzymatic activity.

Tumor cell cytolysis mediated by valorphin, an opioid-like fragment of hemoglobin beta-chain

Valorphin, an endogenous opioid-like hemoglobin fragment, is cytotoxic for L929 and K562 tumor cells in 10(-7)-10(-13) M concentration range. Because cytolytic effects induced by valorphin in K562 cells are inhibited by naloxone, opioid receptors should be involved in induction of valorphin-mediated tumor cell death. Three distinct cytolytic processes, differing in the onset time and the development time, take place with K562 cells within 10-18 h of incubation with valorphin. All three processes are not associated with apoptotic mechanism of cell death.

Alteration of intraerythrocyte proteolytic degradation of hemoglobin during Hodgkin's disease

The erythrocyte lysate samples obtained from 10 healthy donors (aged of 23 +/- 12 years) and 16 patients with Hodgkin's disease (aged of 39 +/- 25 years) with the following histological types: 12 mixed cellularity and 4 nodular sclerosis, were studied. Patients with Hodgkin's disease (HD) were randomly selected before, during or after the completion of combined chemotherapy. A comparative analysis of peptide components of erythrocyte lysate samples of HD patients and healthy donors was carried out. The amino acid sequences of 4 peptides, corresponding to fragments 1-33, 1-32, 1-31 and 1-30 of human hemoglobin (Hb) alpha-chain were determined. Increase of the content of two fragments corresponding to 1-31 and 1-32 amino acid residues of alpha-globin were detected for HD patients. The link between the normal process of proteolytic degradation and those occurring during HD is proposed. The possibility of using the identified alterations recorded during HD diagnosis is discussed.

Proteolytic degradation of hemoglobin in erythrocytes leads to biologically active peptides

A number of hemoglobin-derived homogeneous peptides were isolated from erythrocyte lysate. The amino acid sequences of nine peptides were determined. Seven out of nine peptides were relatively long, 30-32 membered peptides covering the N- or C-terminal sequences of globin chains. The remaining two were the pentapeptide neo-kyotorphin and its tetrapeptide derivative.

Immunoregulatory properties of hexapeptide isolated from porcine bone marrow cell culture

Myelopeptide 1 (MP-1) is hexapeptide originally isolated from porcine bone marrow cell culture. It was synthesized and its immunoregulatory properties were studied. MP-1 caused a 1.5-2-fold dose-dependent increase of antibody production in the culture of mouse immune lymph node cells. It abolished Con A induction of T suppressors in the suspension of mouse spleen cells and counteracted the inhibitory effect of T suppressors on antibody production. The inoculation of MP-1 (1 x 10(-9) g/mouse) to mice two weeks after their gamma-irradiation (2 Gy) resulted in an increase of antibody production up to 80.2 +/- 15.5% as compared to that in the irradiated control 37.6 +/- 12.0%. Immunofluorescent analysis revealed the specific binding of MP-1 with receptors on the target cells in the suspension of mouse spleen cells. It is supposed that MP-1 participates in the immunoregulatory processes in the living organism.

Isolation of a novel peptide with a unique binding profile from human brain cortex: Tyr-K-MIF-1 (Tyr-Pro-Lys-Gly-NH2)

Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2), Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2), and MIF-1 (Pro-Leu-Gly-NH2) are biologically active peptides previously isolated from brain tissue. We now have used size exclusion chromatography and several consecutive rp-HPLC steps monitored by RIA to isolate a structurally related peptide from human brain cortex with the sequence Tyr-Pro-Lys-Gly-NH2 (Tyr-K-MIF-1). Determination of the sequence, electrospray mass spectrometry, and comparison of its chromatographic behavior with synthetic Tyr-K-MIF-1 confirmed the structure. Unlike Tyr-MIF-1 and Tyr-W-MIF-1, Tyr-K-MIF-1 does not bind to the mu opiate site; unlike MIF-1, Tyr-K-MIF-1 can bind to the Tyr-MIF-1 site. Of these peptides, only Tyr-K-MIF-1 binds to its own site in brain tissue prepared in Tris buffer. Thus, a new member of the Tyr-MIF-1 family of peptides, with a unique profile of binding, has been isolated from human brain cortex.

Endogenous opiates: 1992

This paper is the fifteenth installment of our annual review of research concerning the opiate system. It includes papers published during 1992 involving the behavioral, non-analgesic, effects of the endogenous opiate peptides. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal and renal function; mental illness and mood; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; general activity and locomotion; sex, pregnancy, and development; immunological responses; and other behaviors.

Isolation of Tyr-W-MIF-1 from bovine hypothalami

Tyr-W-MIF-1 (Tyr-Pro-Trp-Gly-NH2) was recently isolated from human brain cortex. We have now isolated it from bovine hypothalami by solid phase extraction and several consecutive rpHPLC steps monitored by an RIA originally developed for the endogenous brain peptide Tyr-MIF-1 (Tyr-Pro-Leu-Gly-NH2). Determination of the sequence of the purified material and comparison of its chromatographic behavior with synthetic Tyr-W-MIF-1 confirmed the structure. The synthetic peptide and the isolated material showed almost identical binding to mu opiate receptors.

Isolation of a novel tetrapeptide with opiate and antiopiate activity from human brain cortex: Tyr-Pro-Trp-Gly-NH2 (Tyr-W-MIF-1)

A novel tetrapeptide, Tyr-Pro-Trp-Gly-NH2 (Tyr-W-MIF-1), was purified from extracts of frontal cortex of human brain tissue by several consecutive reversed-phase high performance liquid chromatographic steps followed by a radioimmunoassay originally developed for Tyr-Pro-Leu-Gly-NH2 (Tyr-MIF-1). Sequencing, mass spectrometric analysis, and comparison of its chromatographic behavior with that of the synthetic peptide confirmed the structure. Like Tyr-MIF-1, which was previously isolated from human brain tissue, Tyr-W-MIF-1 can inhibit the binding of 3H-DAMGO (selective for mu opiate receptors) to rat brain and can act as an opiate agonist as well as antagonist. Tyr-W-MIF-1 was a more potent opiate agonist than Tyr-MIF-1, the free acid of Tyr-W-MIF-1, and the structurally related hemoglobin-derived opiate peptide hemorphin-4 (Tyr-Pro-Trp-Thr) in the guinea pig ileum. Each of these peptides acted as opiate antagonists on the ileum from morphine-tolerant guinea pigs; the free acid of Tyr-W-MIF-1 was the most potent antagonist in inhibiting the activity of DAMGO. The results demonstrate the presence in human brain of a new member of the Tyr-MIF-1 family of biologically active peptides.