Biological Activity Of Peptides Research Articles

First transcriptome analysis of the venom glands of the scorpion Hottentotta zagrosensis (Scorpions: Buthidae) with focus on venom lipolysis activating peptides.

Scorpion venom is a rich source of biological active peptides and proteins. Transcriptome analysis of the venom gland provides detailed insights about peptide and protein venom components. Following the transcriptome analysis of different species in our previous studies, our research team has focused on the Hottentotta zagrosensis as one of the endemic scorpions of Iran to obtain information about its venom proteins, in order to develop biological research focusing on medicinal applications of scorpion venom components and antivenom production. To gain insights into the protein composition of this scorpion venom, we performed transcriptomic analysis. Transcriptomic analysis of the venom gland of H. zagrosensis, prepared from the Khuzestan province, was performed through Illumina paired-end sequencing (RNA-Seq), Trinity de novo assembly, CD-Hit-EST clustering, and annotation of identified primary structures using bioinformatics approaches. Transcriptome analysis showed the presence of 96.4% of complete arthropod BUSCOs, indicating a high-quality assembly. From total of 45,795,108 paired-end 150 bp trimmed reads, the clustering step resulted in the generation of 101,180 de novo assembled transcripts with N50 size of 1,149 bp. 96,071 Unigenes and 131,235 transcripts had a significant similarity (E-value 1e-3) with known proteins from UniProt, Swissprot, Animal toxin annotation project, and the Pfam database. The results were validated using InterProScan. These mainly correspond to ion channel inhibitors, metalloproteinases, neurotoxins, protease inhibitors, protease activators, Cysteine-rich secretory proteins, phospholipase A enzymes, antimicrobial peptides, growth factors, lipolysis-activating peptides, hyaluronidase, and, phospholipase D. Our venom gland transcriptomic approach identified several biologically active peptides including five LVP1-alpha and LVP1-beta isoforms, which we named HzLVP1_alpha1, HzLVP1_alpha2, HzLVP1_alpha3, HzLVP1_beta1, and HzLVP1_beta and have extremely characterized here. Except for HzLVP1_beta1, all other identified LVP1s are predicted to be stable proteins (instability index <40). Moreover, all isoform of LVP1s alpha and beta subunits are thermostable, with the most stability for HzLVP1_alpha2 (aliphatic index = 71.38). HzLVP1_alpha2 has also the highest half-life. Three-dimensional structure of all identified proteins compacts with three disulfide bridges. The extra cysteine residue may allow the proteins to form a hetero- or homodimer. LVP1 subunits of H. zagrosensis potentially interact with adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL), two key enzymes in regulation of lipolysis in adipocytes, suggesting pharmacological properties of these identified proteins.

Pathobiochemical effects of oligopeptides in human body

The article is devoted to the study of pathobiochemical effects of short peptides in the human body. Purpose of the work: to summarize and present the material demonstrating the pathobiochemical effects of oligopeptides in the human body. Methods and materials: a search of literature by Russian and foreign authors was performed; the obtained data were analyzed and summarized. Results. General information characterizing the pathobiochemical effects of oligopeptides in the human body is given. The main mechanisms of interaction of oligopeptides with cells are described. Conclusion. The biological activity of peptides is realized at various structural levels due to the physicochemical processes of interaction between oligopeptides and body cells. The high physiological activity of these molecules suggests the prospects for their fur ther use.

Characterization of Novel Cell-Adhesive Peptides for Biomaterial Development.

In previous studies, my group developed cell-adhesive peptide-polysaccharide complexes as biomaterials for tissue engineering. Having a wide variety of cell-adhesive peptides is important as the biological functions of peptide-polysaccharide complexes are highly dependent on the biological activity of peptides. This paper reviews the biological activities of two types of recently characterized cell-adhesive peptides. The first is peptides rich in basic amino acids originating from octaarginine. We analyzed the relationships between the amino acid composition of basic peptides and cell adhesion, elongation, and proliferation and identified the most suitable peptide for cell culture. The second was arginine-glycine-aspartic acid (RGD)-containing peptides that promote the adhesion of induced pluripotent stem cells (iPSCs). We identified the RGD-surrounding sequences necessary for iPSC adhesion, clarified the underlying mechanism, and improved cell adhesion by modifying the structure-activity relationships. The novel cell-adhesive peptides identified in our previous studies may aid in the development of novel peptide-based biomaterials.

РАЗРАБОТКА С ИСПОЛЬЗОВАНИЕМ МОЛЕКУЛЯРНОЙ ПЕПТИДНОЙ ТРАНСПЛАНТАЦИИ ПОТЕНЦИАЛЬНОГО НЕЙРОПРОТЕКТОРНОГО БИОПЕПТИДА

The present research is focused on design of new nutritional neuroprotective biopeptide, using method of molecular peptide transplantation (MPT) based on analysis of literature sources, databases on biophysical properties and biological activity of peptides. The objects of the research are sequences of amino acid residues of peptides with proven neuroprotective properties. Prediction of biological activity of the developed biopeptide was carried out using the Peptide Ranker database (http://distilldeep.ucd.ie/PeptideRanker). Information on cyclic peptides frameworks that are resistant to proteolysis was obtained in the Cybase database (http://www.cybase.org.au), biopeptide identification was carried out using the EROP-Moscow database (http://erop.inbi.ras.ru/index.html), biophysical properties assessment of the developed biopeptide was carried out using the PepCalc peptide properties calculator (http://pepcalc.com) and APD 3 databases (https://aps.unmc.edu/home). A neuro-protective interfering peptide has been developed by preliminary preparation of a cyclotide-based framework followed by insertion of short HFRWPGP peptide into the framework by the MPT method. The developed peptide has the following sequence of amino acid residues: PCRRRCHFRWPGPCRGRCP, has high biological activity equal to 0.89. The hydrophobicity of the peptide according to Wimley-White in the whole residue is 2.91, therefore, the peptide is well soluble in water. The protein binding potential (Boman index) is high and is 4.3 kcal / mol, indicating its ability to bind to target receptors.

Protein Hydrolysates from Fishery Processing By-Products: Production, Characteristics, Food Applications, and Challenges.

Fish processing by-products such as frames, trimmings, and viscera of commercial fish species are rich in proteins. Thus, they could potentially be an economical source of proteins that may be used to obtain bioactive peptides and functional protein hydrolysates for the food and nutraceutical industries. The structure, composition, and biological activities of peptides and hydrolysates depend on the freshness and the actual composition of the material. Peptides isolated from fishery by-products showed antioxidant activity. Changes in hydrolysis parameters changed the sequence and properties of the peptides and determined their physiological functions. The optimization of the value of such peptides and the production costs must be considered for each particular source of marine by-products and for their specific food applications. This review will discuss the functional properties of fishery by-products prepared using hydrolysis and their potential food applications. It also reviews the structure-activity relationships of the antioxidant activity of peptides as well as challenges to the use of fishery by-products for protein hydrolysate production.

Antioxidant and Renin Inhibitory Activities of Peptides from Food Proteins on Hypertension: A Review.

Hypertension is a condition induced by oxidative stress causing an alteration in the endothelium, which increases the risk of suffering from other degenerative diseases. This review compiles the findings on peptides from food proteins with antioxidant and antihypertensive activities. Antihypertensive peptides are mainly focused on renin inhibition. Peptides containing hydrophobic amino acids have antioxidant and renin inhibitory activities, as reported by studies on the biological activity of peptides from various food sources evaluated separately and simultaneously. Peptides from food sources can present multiple biological activities. Moreover, antioxidant peptides have the potential to be evaluated against renin, offering an alternative for hypertension therapy without causing adverse side effects.

Targeted and selective knockout of the TLQP-21 neuropeptide unmasks its unique role in energy homeostasis

ObjectivePro-peptide precursors are processed into biologically active peptide hormones or neurotransmitters, each playing an essential role in physiology and disease. Genetic loss of function of a pro-peptide precursor results in the simultaneous ablation of all biologically-active peptides within that precursor, often leading to a composite phenotype that can be difficult to align with the loss of specific peptide components. Due to this biological constraint and technical limitations, mice carrying the selective ablation of individual peptides encoded by pro-peptide precursor genes, while leaving the other peptides unaffected, have remained largely unaddressed. MethodsWe developed and characterized a mouse model carrying the selective knockout of the TLQP-21 neuropeptide (ΔTLQP-21) encoded by the Vgf gene. To achieve this goal, we used a knowledge-based approach by mutating a codon in the Vgf sequence leading to the substitution of the C-terminal Arginine of TLQP-21, which is the pharmacophore as well as an essential cleavage site from its precursor, into Alanine (R21→A). ResultsWe provide several independent validations of this mouse, including a novel in-gel digestion targeted mass spectrometry identification of the unnatural mutant sequence, exclusive to the mutant mouse. ΔTLQP-21 mice do not manifest gross behavioral and metabolic abnormalities and reproduce well, yet they have a unique metabolic phenotype characterized by an environmental temperature-dependent resistance to diet-induced obesity and activation of the brown adipose tissue. ConclusionsThe ΔTLQP-21 mouse line can be a valuable resource to conduct mechanistic studies on the necessary role of TLQP-21 in physiology and disease, while also serving as a platform to test the specificity of novel antibodies or immunoassays directed at TLQP-21. Our approach also has far-reaching implications by informing the development of knowledge-based genetic engineering approaches to generate selective loss of function of other peptides encoded by pro-hormones genes, leaving all other peptides within the pro-protein precursor intact and unmodified.

Self-assembled peptide nanoparticles for photodynamic therapy: morphological and mechanical effects on hepatocellular carcinoma cells

Self-assembling peptides, offering favorable biocompatibility, high stability, and easy incorporation of various functionalities, have demonstrated enormous potential for the precise design of next-generation nanodrugs for non-invasive tumor therapy. Peptide-based supramolecular photodynamic therapy (PDT) has shown great promise as an emerging modality for cancer treatment, achieving substantially-enhanced photosensitizer delivery selectivity and treatment efficacy, based on peptide biological activity and self-assembly potential. Although considerable research has been conducted toward fabricating self-assembling peptide-based smart nanodrugs for PDT, few studies have investigated cellular biophysical responses as indicators of tumor function and metabolic state. Here, via atomic force microscopy (AFM)-based morphological and mechanical measurements, including optical microscopy and scanning electron microscopy, we observed, for the first time, variation in membrane stiffness of human liver (HepG2) cancer cells treated with self-assembling peptides serving as a PDT nanodrug. This biophysical information will help to establish a comprehensive understanding of the anticancer effect of peptide-based smart nanodrugs, and highlight the exceptional ability of AFM in determining cell-surface properties.

Kisspeptin receptor in GtoPdb v.2023.1

The kisspeptin receptor (nomenclature as agreed by the NC-IUPHAR Subcommittee on the kisspeptin receptor [11]), like neuropeptide FF (NPFF), prolactin-releasing peptide (PrP) and QRFP receptors (provisional nomenclature) responds to endogenous peptides with an arginine-phenylalanine-amide (RFamide) motif. kisspeptin-54 (KP54, originally named metastin), kisspeptin-13 (KP13) and kisspeptin-10 (KP10) are biologically-active peptides cleaved from the KISS1 (Q15726) gene product. Kisspeptins have roles in, for example, cancer metastasis, fertility/puberty regulation and glucose homeostasis.

Multiple Modes of Zinc Binding to Histatin 5 Revealed by Buffer-Independent Thermodynamics.

Histatin 5 (Hist5) is an antimicrobial peptide found in human saliva as part of the innate immune system. Hist5 can bind several metal ions in vitro, and Zn2+ has been shown to function as an inhibitory switch to regulate the peptide's biological activity against the opportunistic fungal pathogen Candida albicans in cell culture. Here, we studied Zn2+ binding to Hist5 at four temperatures from 15 to 37 °C using isothermal titration calorimetry to obtain thermodynamic parameters that were corrected for competing buffer effects. Hist5 bound Zn2+ with a buffer-dependent association constant of ∼105 M-1 and a buffer-independent association constant of ∼6 × 106 M-1 at pH 7.4 and at all temperatures tested. Zn2+ binding was both enthalpically and entropically favorable, with larger entropic contributions at 15 °C and larger enthalpic contributions at 37 °C. Additionally, the Zn:Hist5 binding stoichiometry increased from 1:1 to 2:1 as temperature increased. The enthalpy-entropy compensation and the variable stoichiometry lead us to propose a model in which the Zn-Hist5 complex exists in an equilibrium between two distinct binding modes with different Zn:Hist5 stoichiometries. The in-depth thermodynamic analysis presented herein may help illuminate the biophysical basis for Zn-dependent changes in the antifungal activity of Hist5.

The mechanism underlying toxicity of a venom peptide against insects reveals how ants are master at disrupting membranes

Hymenopterans represent one of the most abundant groups of venomous organisms but remain little explored due to the difficult access to their venom. The development of proteo-transcriptomic allowed us to explore diversity of their toxins offering interesting perspectives to identify new biological active peptides. This study focuses on U9 function, a linear, amphiphilic and polycationic peptide isolated from ant Tetramorium bicarinatum venom. It shares physicochemical properties with M-Tb1a, exhibiting cytotoxic effects through membrane permeabilization. In the present study, we conducted a comparative functional investigation of U9 and M-Tb1a and explored the mechanisms underlying their cytotoxicity against insect cells. After showing that both peptides induced the formation of pores in cell membrane, we demonstrated that U9 induced mitochondrial damage and, at high concentrations, localized into cells and induced caspase activation. This functional investigation highlighted an original mechanism of U9 questioning on potential valorization and endogen activity in T. bicarinatum venom.

A software tool for data mining of physicochemical properties of peptides

Biologically active peptides (BAP) are increasingly in the focus of scientific research due to their widespread use in medicine, food and pharmaceutical industries. Researching and studying the properties of peptides is a laborious and expensive process. In recent years, in silico methods, including data mining or artificial intelligence, have been applied more and more to reveal biological, physicochemical and sensory properties of peptides. This significantly shortens the process of peptide sequences analysis. This article presents a software tool that uses a data mining approach to discover a number of physicochemical properties of a specific peptide. Working with it is extremely simple - it is only necessary to input the amino acid sequence of the peptide of interest. The software tool is designed to generate data in order to increase the classification and prediction accuracy, as well as to leverage the engineering of new amino acid sequences. This way, the proposed software greatly facilitates the work or scientific researchers. The software application is publicly available at www.pep-lab.info/dmpep.

Zika Virus NS2B-NS3 Protease: Quantum Chemical Properties Insights into Designing Inhibitory Peptides.

Zika fever affects poor and vulnerable populations, presenting cycles observed in, at least 86 countries, with no vaccine prevention or treatment available. It is known that the genus Flavivirus causes Zika Virus (ZIKV), as Dengue and Yellow Fever, whose genetic material decodes, among other proteins, a series of non-structural (NS) proteins essential for viral replication, such as NS2B-NS3 protease. Additionally, chemical and biological systems are commonly studied using molecular modeling approaches allowing, among several other processes, to elucidate mechanisms of action, molecule reactivity and/or chemical properties and the design of new drugs. Thus, considering the in silico complexes between the biological target and the bioactive molecule, it is possible to understand better experimental results based on molecular properties, which are compared with the findings of the biological activity. Accordingly, this study aimed to present computational docking simulations of five previously reported active peptides against NS2B-NS3 protease of ZIKV and analyze some quantum chemical properties to identify the main contribution to improving the action. The compounds were described by Rut and coworkers (2017) and Hill and coworkers (2018), submitted to docking simulation in Gold software and quantum chemical properties calculations in Wavefunction Spartan software. Total energy, electrophilicity index (ω) and energy gap (GAP) appeared to be the best properties to justify the peptide's biological activity. Moreover, the most promising compound (P1, Km 4.18 μM) had the best value of total energy (- 2763.04001 au), electrophilicity index (8.04 eV) and GAP (6.49 eV), indicating an energetically favorable molecule with good interaction with the target and, when compared to other peptides, presented moderate reactivity. P4 showed the highest electrophilicity index value (28.64 eV), which justified the interaction ability visualized in the docking simulation. However, its GAP value (4.24 eV) was the lowest in the series, suggesting high instability, possibly validating its low biological activity value (Km 19 uM). GAP was important to understand the chemical instability, and high values can promote damage to biological response. Furthermore, it was also noted that high electron affinity, related to the electrophilicity index, promoted electron-accepting characteristics, which was important to improve the biological activity of the peptides. A larger compound series must be studied to access features more precisely. However, these results have paramount importance in guiding future effort in this extremely-need health area.

Prediction of Aggregation of Biologically-Active Peptides with the UNRES Coarse-Grained Model.

The UNited RESidue (UNRES) model of polypeptide chains was applied to study the association of 20 peptides with sizes ranging from 6 to 32 amino-acid residues. Twelve of those were potentially aggregating hexa- or heptapeptides excised from larger proteins, while the remaining eight contained potentially aggregating sequences, functionalized by attaching larger ends rich in charged residues. For 13 peptides, the experimental data of aggregation were used. The remaining seven were synthesized, and their properties were measured in this work. Multiplexed replica-exchange simulations of eight-chain systems were conducted at 12 temperatures from 260 to 370 K at concentrations from 0.421 to 5.78 mM, corresponding to the experimental conditions. The temperature profiles of the fractions of monomers and octamers showed a clear transition corresponding to aggregate dissociation. Low simulated transition temperatures were obtained for the peptides, which did not precipitate after incubation, as well as for the H-GNNQQNY-NH2 prion–protein fragment, which forms small fibrils. A substantial amount of inter-strand β-sheets was found in most of the systems. The results suggest that UNRES simulations can be used to assess peptide aggregation except for glutamine- and asparagine-rich peptides, for which a revision of the UNRES sidechain–sidechain interaction potentials appears necessary.

Low allergenic fermented drink enriched with bioactive peptides of whey proteins

Whey protein hydrolysates are most often used in the production of hypoallergenic products, as low molecular weight proteolysis products do not cause allergic reactions in consumers. However, it has been found that whey proteins are not only a good source of amino acids, but also a large number of natural biologically active peptides (BAP). They are formed during normal digestion in the gastrointestinal tract. These natural BAP have a positive effect on various functions of the human body regardless of age. When using microbial and plant enzyme preparations, as well as hydrolysis conditions other than physiological, the formation of such biologically active peptides is impossible, and such products lose much of their biological value. The article highlights the results of research on the development of technology of low-allergenic fermented drink enriched with biologically active peptides of whey proteins. To develop the technology of beverage, we proposed to use micellar casein, which is a source of basic milk protein – casein and whey protein hydrolysate, obtained in physiological conditions, as a source of biologically active peptides from whey proteins. Whey protein hydrolysate was added to the product in two ways: to the normalized mixture before and after fermentation. The hydrolysate was added to the product in an amount corresponding to the whey protein content: 0.5 %; 0.7 %; 0.9 %; 1.1 %. It was found that the amount of hydrolysate introduced affects the duration of fermentation of the studied samples. It was noted that until the end of the recommended shelf life, the organoleptic characteristics of samples fermented with hydrolysate remained virtually unchanged, while the consistency of samples in which the hydrolysate was added after fermentation became slightly thinner compared to the day of production. It is also proved that the usage of whey protein hydrolysate helps to reduce the release of whey when filtering a fermented beverage during storage for seven days.

Molecular design and biological activity analysis of antimicrobial peptide RIKL

Natural antimicrobial peptides have strong bactericidal activities. An obstacle of the development of antimicrobial peptides resides in the difficulty of developing peptides with high biocompatibility. In this study, molecular dynamics analysis was employed to assess the structural characteristics and biological activities of peptides. A (RXKY)2(YRY)2 structure was used as a template to design an antimicrobial peptide RIKL of high-efficiency and low-toxicity, where X represents Ile and Y represents Leu. The secondary structure of the antimicrobial peptide was detected by circular dichroism (CD), and the structures of RIKL in water and in POPC/POPG membrane environment were measured using molecular dynamics. The biological activity of RIKL was further studied by assessing its antimicrobial activity, hemolytic activity, eukaryotic cytotoxicity, and salt ion stability. CD results showed that RIKL presented an α-helical structure in a simulated bacterial membrane environment. Molecular dynamics simulation predicted that the secondary structure of RIKL could be partly retained in water and POPG environment, while this secondary structure was weakened in the POPC environment. Antimicrobial test suggested that RIKL had high antimicrobial activities, and the geometric mean of the Minimum Inhibitory Concentration (MIC) was 3.1 μmol/L. The hemolysis indicated that RIKL had no hemolytic activity within the detection range, and cytotoxicity test suggested the cytotoxicity of RIKL was low. Stability test showed that RIKL maintained antimicrobial activities under different pH, serum concentrations and salt environments. Based on the above results, RIKL has high cell selectivity and has the potential as a highly effective antibacterial drug.

Effect of willow herb (Epilobium angustifolium L.) extract addition to canned meat with reduced amount of nitrite on the antioxidant and other activities of peptides.

The present study aimed to evaluate the effect of the addition of various amounts (50, 100, 150 and 1000 mg kg-1) of E. angustifolium L. extracts on the biological activity of peptides in canned meat with reduced amount of sodium nitrite and their stability during 180 days of storage (4 °C). The initial peptide data were collected by LC/MS. Antioxidant activities of peptide extracts were detected on the basis of ABTS˙*, FRAP, and iron(II) chelating activity in in vitro tests. A computational study (based on the BIOPEP-UWM database and INNOVAGEN, PeptideRanker and PROTPARAM tools) was also performed to assist in the interpretation of results. The addition of E. angustifolium L. extracts has a positive effect on the peptide profile and various biological activities, the results of which depend on the amount of the extract added to the meat product. However, it should be remembered that the differences between in silico and in vitro experimental environments necessitate further research to confirm the antioxidant behavior of canned meat products supplemented with E. angustifolium L. extract under physiological conditions. Other interactions between the peptide and the food matrix should also be considered as these can lead to chemical and structural modifications that can affect the bioavailability of the bioactive peptides.

Potential Biological Activities of Peptides Generated during Casein Proteolysis by Curly Kale (Brassica oleracea L. var. sabellica L.) Leaf Extract: An In Silico Preliminary Study.

This study is a brief report on the proteolytic activity of curly kale leaf extract against casein. Casein degradation products and an in silico analysis of the biological activity of the peptides obtained was performed. The efficiency of casein hydrolysis by curly kale extract was determined using SDS–PAGE and by peptide concentration determination. The pattern of the enzymatic activity was determined by MALDI–TOF MS analysis. The results showed that α- and β-casein were more resistant to curly kale extract hydrolysis, whereas κ-casein was absent in the protein profile after 8 h of proteolysis, and all casein fractions were completely hydrolyzed after 24 h of incubation. Based on sequence analysis, seven peptides were identified, with molecular mass in the range of 1151–3024 Da. All the peptides were products of β-casein hydrolysis. The identified amino acid sequences were analyzed in BIOPEP, MBPDB, and FeptideDB databases in order to detect the potential activities of the peptides. In silico analysis suggests that the β-casein-derived peptides possess sequences of peptides with ACE inhibitory, antioxidant, dipeptidyl peptidase IV inhibitory, antithrombotic, immunomodulatory, and antiamnesic bioactivity. Our study was first to evaluate the possibility of applying curly kale leaf extract to generate biopeptides through β-casein hydrolysis.

In silico study to predict potential precursors of human dipeptidyl peptidase-IV inhibitors from hazelnut

Chinese hazelnut was chosen to become a probable precursor of biological active peptides via computer simulations in this article. There were a large number of bioactive peptides in Chinese hazelnut sequences according to analytical results from the BIOPEP database. The most prominent of these was the inhibitory peptide for dipeptidyl peptidase-IV (DPP-IV; EC 3.4.14.5), which can be used to treat type 2 diabetes, so the theoretical method to obtain DPP-IV inhibitory peptides by hydrolysis with a single or combination of enzymes was studied. Cytotoxicity analysis performed by ToxinPred showed that all of the DPP-IV inhibitory peptides generated from protein hydrolysis were not cytotoxic. Structural interaction fingerprint analysis revealed that Asp663 and Phe357 may be important residues for ligand binding. In order to further understand the inhibitory mechanism of peptide, VR with lowest half maximum inhibitory concentration (IC50) and IPI (inhibitors have been reported) were selected as ligand of DPP-IV to perform steered molecular dynamics simulations and PMF calculations. The results showed that P1 is the preferred (un)binding tunnel for the inhibitors obtained. Our findings help in the development of new DPP-IV inhibitors which were derived from common food. Communicated by Ramaswamy H. Sarma

Short carboxyl terminal parathyroid hormone peptides modulate human parathyroid hormone signaling in mouse osteoblasts

BackgroundNovel human parathyroid hormone (hPTH) peptides of unknown biological activity have recently been identified in the serum of subjects with normal renal function, chronic renal failure, and end-stage renal disease through the application of liquid chromatography-high resolution mass spectrometry. Purposeof experiments: To determine the bioactivity of these peptides, we synthesized hPTH28-84, hPTH38-84, and hPTH45-84 peptides by solid phase peptide synthesis and tested their bioactivity in MC3T3-E1 mouse osteoblasts, either individually or together with the native hormone, hPTH1-84, by assessing the accumulation of 3´,5´-cyclic adenosine monophosphate (cAMP) and the induction of alkaline phosphatase activity. ResultsIncreasing doses of hPTH1-84 (1–100 nM) increased the accumulation of cAMP and alkaline phosphatase activity in osteoblasts. hPTH28-84, hPTH38-84, and hPTH45-84 in concentrations of 1–100 nM were biologically inert. Surprisingly, 100 nM hPTH38-84 and hPTH45-84 increased the accumulation of cAMP in osteoblasts treated with increasing amounts of hPTH1-84. Human PTH28-84 had no effects on cAMP activity alone or in combination with hPTH1-84. Conversely, 100 nM hPTH38-84, hPTH45-84, and hPTH28-84 blocked the activation of alkaline phosphatase activity by hPTH1-84. ConclusionsThe data show that the short carboxyl-terminal hPTH peptides, hPTH38-84 and hPTH45-84, increase the amount of cellular cAMP generated in cultured osteoblasts in response to treatment with full-length hPTH1-84 when compared to full-length hPTH1-84 alone. Human PTH28-84 had no effect on cAMP activity alone or in combination with hPTH1-84. Human PTH28-84, hPTH38-84 and hPTH45-84 reduced the effects of hPTH1-84 in osteoblasts with respect to the induction of alkaline phosphatase activity compared to hPTH1-84 alone. Short carboxyl peptides of human PTH are biologically inert but when administered together with full-length hPTH1-84 modulate the bioactivity of hPTH1-84 in osteoblasts.