Lipolysis of ApoC-II deficient very low density lipoproteins: enhancement of lipoprotein lipase action by synthetic fragments of apoC-II.

Enzymic hydrolysis of triacylglycerol has been studied with very low density lipoproteins from an individual with a genetically determined absence of apoC-II, the activator apoprotein for lipoprotein lipase. Normal rates of ester cleavage by purified bovine milk lipoprotein lipase can be achieved $\text{in}\text{vitro}$ with native apoC-II and by three shorter synthetic peptides, apoC-II(55–78), apoC-II(50–78) and apoC-II(43–78), which contain part of the carboxyl terminal third of the native apoprotein. At 0.5 μM concentration, all peptides produced a 7-fold activation. ApoC-II(43–78), but not apoC-II(50–78) or apoC-II(55–78), could bind VLDL as shown by separation of unbound ¹²⁵I peptides and the lipoproteins. Thus, residues 43–50 of apoC-II are part of a lipid binding region. High affinity binding of apoC-II peptides to the lipoprotein substrate is not obligatory for activation of lipoprotein lipase.     

The Status of the Hemostasis System under the Influence of Proline Peptides during the Development of Experimental Metabolic Syndrome

A comparative study of the influence of regulatory proline peptides Pro–Gly–Pro, Pro–Arg–Pro, Pro–Gly–Pro–Leu, and Arg–Pro–Gly–Pro on the state of the hemostasis system was carried out in an experiment on male rats with metabolic syndrome. Under these conditions, repeated (7-fold) intranasal administration of the peptides in a daily dose of 50 μg/kg resulted in an increase in the anticoagulant potential of the blood, namely, in an increase in the anticoagulant, fibrinolytic, and antiplatelet activity 20 h and 7 days after the last peptide injection. The arginine–containing peptide Arg–Pro–Gly–Pro had the most pronounced and stable effect on haemostasis under these experimental conditions.     

Peptide-Induced Morphogenesis in the Nematode-Trapping Fungus Arthrobotrys oligospora

The present investigation shows the ability of peptides to induce capture organ formation in Arthrobotrys oligospora when applied in a synthetic low nutrient medium. Under certain conditions casitone was shown to induce capture organ formation. The active principle in casitone was concentrated and purified by alternating procedures of ion exchange chromatography and gel chromatography in pyridine-acetic acid buffers. Crude casitone solutions were applied to columns of Dowex 50 W-X2 and eluted stepwise with 0.1–1.0 M pyridine-acetic acid pH 3.2–5.1. Active portions, free from most acid and neutral amino acids, were further purified on columns of Sephadex G-10 in 0.1 M pyridine-acetic acid pH 4.6. Aromatic amino acids and large molecules in the void volume could be separated from an active peptide mixture which was subjected to renewed ion exchange chromatography on Bio-Rad AG 50 W-X2. By stepwise and/or gradient elution in 0.1–0.5 M pyridine-acetic acid pH 3.2 fairly purified peptides were obtained. The composition of the test medium is an important factor in spontaneous capture organ formation. The peptides isolated from casitone induced capture organ formation, when given to the fungus in a synthetic mineral salt medium supplied with thiamin and biotin. Similar effects were obtained with small synthetic peptides in the same concentration (0.1 mg/ml). A large variety of peptides seem to be active when applied in a suitable medium. This was especially true for peptides with Rf > Rf_leu on thin layers of cellulose developed with butanol-acetic acid-water (4: 1: 1). Of the peptides investigated valyl-peptides exerted the most drastic effect.     

Production of Angiotensin-I-Converting-Enzyme-Inhibitory Peptides in Fermented Milks (<Emphasis Type="Italic">Lassi</Emphasis>) Fermented by <Emphasis Type="Italic">Lactobacillus acidophillus</Emphasis> with Consideration of Incubation Period and Simmering Treatment

The lassi, fermented milks product containing angiotensin-I-converting-enzyme (ACE)-inhibitory peptides were produced by using selected Lactobacillus acidophilus NCDC-15 and the incubation period and simmering effect was also optimized for production of ACE-inhibitory peptides. The time–temperature combination for the heat treatment was optimized using RSM. The biological activity was measured in the supernatant of the fermented milk after centrifugation. The lowest IC₅₀ values for the inhibition of angiotensin-converting enzyme (ACE) was found 28.9 ± 0.95 μg protein/ml in the supernatant of milk fermented by L. acidophilus and heated at 78 °C for 10 h. The fractions which showed the highest ACE-inhibitory indexes were further purified by different techniques including solid phase extraction, RP-HPLC and FPLC and the related peptides were identified by LC–MS/MS using the Ultimate 3000 nano HPLC system (Dionex) coupled to a 4000 Q TRAP electro-spray ionization mass spectrometry. The high ACE-inhibitory activity containing fractions of the milk fermented by L. acidophilus contained the sequences of b-casein (b-CN) fragment. The fraction-III showed minimum IC₅₀ value i.e. 14.57 ± 0.72 μg/ml compared with fraction-I and fraction-II. Among these peptides 14 peptides have been identified from the fraction-I of the lassi prepared from L. acidophilus i.e. β-CN f47–56, β-CN f47–57, β-CN f199–209, β-CN f176–182, β-CN f176–183, β-CN f176–184, β-CN f1–7, β-CN f57–68, β-CN f166–175, β-CN f195–206, β-CN f195–207, β-CN f195–209, β-CN f94–106 and β-CN f169–176 showed partially or completely homology to that the milk protein bioactive peptides having ACE inhibitory. The two peptides KVLPVPQK (β-CN f169–176) and YQEPVLGPVRGPFPIIV (β-CN f193–209) have the same sequence as ACE inhibitory peptides (Maeno et al. in J Dairy Sci 79(8):1316–1321, 1996; Yamamoto et al. in J Dairy Sci 77:917–922, 1994b).     

Preparation and characterization of novel bioactive peptides responsible for angiotensin I‐converting enzyme inhibition from wheat germ

Reported is the preparation of wheat germ (WG) hydrolyzate with potent angiotensin I‐converting enzyme (ACE) inhibitory activity, and the characterization of peptides responsible for ACE inhibition. Successful hydrolyzate with the most potent ACE inhibitory activity was obtained by 0.5 wt.%–8 h Bacillus licheniformis alkaline protease hydrolysis after 3.0 wt.%–3 h α‐amylase treatment of defatted WG (IC₅₀; 0.37 mg protein ml⁻¹). The activity of WG hydrolyzate was markedly increased by ODS and subsequent AG50W purifications (IC₅₀; 0.018 mg protein ml⁻¹). As a result of isolations by high performance liquid chromatographies, 16 peptides with the IC₅₀ value of less than 20 μm , composed of 2–7 amino acid residues were identified from the WG hydrolyzate. Judging from the high content (260 mg in 100 g of AG50W fraction) and powerful ACE inhibitory activity (IC₅₀; 0.48 μm ), Ile‐Val‐Tyr was identified as a main contributor to the ACE inhibition of the hydrolyzate. Copyright © 1999 European Peptide Society and John Wiley & Sons, Ltd.     

Antigenic structure of human hemoglobin: Delineation of the antigenic site (site 2) within region 41–65 of the alpha chain by immunochemistry of synthetic peptides

A comprehensive synthetic approach consisting of a series of consecutive, uniform overlapping peptides encompassing the entire protein chain was recently used to determine the full antigenic profile of the α-chain of human hemoglobin (Hb). The peptides synthesized enabled the localization of five major “continuous” antigenic regions within the α chain. The present findings describe the delineation of an antigenic site (site 2) residing within the region 41–65. Ten peptides representing the α-chain regions 41–55, 51–65, 45–54, 45–56, 45–58, 45–60, 48–56, 49–56, 50–56, and 51–56 were synthesized and purified. Quantitative radioimmunoadsorbent titrations were used to determine binding to peptide adsorbents of radioiodinated anti-Hb antibodies that were raised in rabbit, goat, and outbred mouse. In one set of peptides, the N-terminal was fixed while the C-terminal end was increased by increments of two residues from Gln-54 to Lys-60 (i.e., peptides 45–54, 45–45, 45–58, and 45–60). Binding studies revealed that maximum antibody activity resided in peptide 45–45, indicating that Lys-56 marks the C-terminal boundary of the site. In the second set of peptides, the C-terminal was fixed at Lys-56 while the peptides were elongated at their N-terminal by one-residue increments from Gly-51 to Leu-48. Antibody-binding studies with these peptides indicated that Ser-49 defines the N-terminal boundary of the site. Therefore, the antigenic site within region 41–65 of the α chain comprises residues 49–56. The relevance of these findings to the immune recognition of Hb and other proteins is discussed.     

Use of fluorescamine in the chromatographic analysis of peptides from proteins

A routine procedure for the fluorometric analyses of peptides in the column chromatographic fraction has been described. Sensitivities of detection are 3–5 times higher in the direct fluorescamine method and 6–50 times higher in the method with alkaline hydrolysis than the conventional ninhydrin color method with hydrolysis (11).Reactivity of peptides with fluorescamine appears to depend mainly on the nature of amino acids occupying the amino termini; ?-amino groups of lysine residues in the peptides tested have been found not to contribute significantly in yielding fluorescence in the reaction.     

Capillary zone electrophoresis of collagen type I CNBr peptides in acid buffers

Collagen type-I CNBr peptides were separated under acidic conditions by capillary electrophoresis. Separation conditions were: 100 mM phosphate buffer pH 2.5, 50 cm × 50 μm capillary (placed in a cartridge), 8 kV, running time 30–45 min, detection by UV at 200 nm. The peptides were separated strictly by their molecular mass and the overall pattern was well comparable to RP-HPLC separations of these analytes. It is proposed that the separation mechanism may involve hydrophobic sorptions to the capillary wall.     

In silico identification of novel ACE and DPP-IV inhibitory peptides derived from buffalo milk proteins and evaluation of their inhibitory mechanisms

The capacity of buffalo milk proteins to release bioactive peptides was evaluated and novel bioactive peptides were identified. The sequential similarity between buffalo milk proteins and their cow counterparts was analysed. Buffalo milk proteins were simulated to yield theoretical peptides via in silico proteolysis. The potential of selected proteins to release specific bioactive peptides was evaluated by the A value obtained from the BIOPEP–UWM database (Minkiewicz et al. in Int J Mol Sci 20(23):5978, 2019). Buffalo milk protein is a suitable precursor to produce bioactive peptides, particularly dipeptidyl peptidase IV (DPP-IV) and angiotensin I-converting enzyme (ACE) inhibitory peptides. Two novel ACE inhibitory peptides (KPW and RGP) and four potential DPP-IV inhibitory peptides (RGP, KPW, FPK and KFTW) derived from in silico proteolysis of buffalo milk proteins were screened using different integrated bioinformatic approaches (PeptideRanker, Innovagen, peptide-cutter and molecular docking). The Lineweaver–Burk plots showed that KPW (IC₅₀?=?136.28?±?10.77 μM) and RGP (104.72?±?8.37 μM) acted as a competitive inhibitor against ACE. Similarly, KFTW (IC₅₀?=?873.92?±?32.89 μM) was also a competitive inhibitor of DPP-IV, while KPW and FPK (82.52?±?10.37 and 126.57?±?8.45 μM, respectively) were mixed-type inhibitors. It should be emphasized that this study does not involve any clinical trial.

     

ACE Inhibitory and Antioxidant Activities of Novel Peptides from <Emphasis Type="Italic">Scorpaena notata</Emphasis> By-product Protein Hydrolysate

This study describes the isolation of angiotensin I converting enzyme and antioxidative peptides from head protein hydrolysate of red scorpionfish (Scorpaena notata) prepared by treatment with a protease from the fungus Penicillium digitatum. After ultrafiltration, three peptides were isolated by a two-step procedure: size exclusion chromatography on a Toyopearl HW-40 followed by reversed-phase high performance liquid chromatography (RP-HPLC) with a high purification yield of 2.22 mg of peptide/g of initial protein. Active peptides were then identified by nanoscale liquid chromatography coupled to tandem mass spectrometry (nanoLC/MS–MS), corresponding to the following sequences: Gln–Gln–Pro–His–Ser–Arg–Ser–Lys–Gly–Phe–Pro–Gly–Pro (1424.724 Da), Gly–Gln–Lys–Ser–Val–Pro–Glu–Val–Arg (1000.565 Da) and Val–Glu–Gly–Lys–Ser–Pro–Asn–Val (830.448 Da). Peptides D-I, E-I and F-I showed high angiotensin-I converting enzyme inhibitory activity with an IC₅₀ values of 0.98, 1.69 and 1.44 µM, respectively as well as a synergistic antioxidant activity between the different fractions. Thus, we have demonstrated that underutilized wastes can be valorized by production of peptides that can be used as potential therapeutic compounds active against oxidative stress and hypertension.     

A new variant of glycogen storage disease type I probably due to a defect in the glucose-6-phosphate transport system.

The amino acid sequence of the respiratory protein, hemerythrin, from $\text{Phascolopsis}\text{gouldii}$ was reinvestigated in the region of residue 58. Sequenator analyses were performed on peptide 50–113, obtained by trypsin digestion of the intact protein, and on peptide 50–62, obtained by cyanogen bromide cleavage of peptide 50–113. In both peptides residue 58 was unambiguously identified as glutamic acid and residue 59 as glutamine. This corrects a previous mistake in the assignment of residue 58 and makes its proposed role as an iron ligand more plausible.     

The relationship between micelle formation and biological activity of peptide 562–572 of luteinizing hormone receptor modified with decanoyl radicals

Lipophilic derivatives of peptides corresponding to cytoplasmic regions of G protein-coupled receptors (GPCR) can act as intracellular agonists. Our previous work showed that peptides corresponding to residues 562–572 of luteinizing hormone receptor and modified with palmitate or decanoate at the C-terminus activate adenylate cyclase in rat testes. The stimulating effect of peptide 562–572 modified with decanoates at both the N- and the C-termini (peptide IV) reached its maximum at the peptide concentration of 10^–5 M and diminished with further increase in its concentration. It was supposed that this effect was due to peptide IV ability to form micelles. To verify this hypothesis, the relationship between biological activity, hydrophobicity, and ability to form micelles was investigated for peptide IV and other acylated derivatives of peptide 562–572, including those carrying C-terminal decanoate (peptide III) and palmitate (peptide VI) moieties. It was found that the stimulating effect of peptide IV taken in the concentration of 10^–5 M on adenylate cyclase activity in plasma membranes of rat testes and ovaries was only slightly lower than that of peptide VI and higher than the effect of peptide III. At the concentration of 10^–3 M, the effect of peptide IV was 20–27% lower and amounted to only 50–51 and 87–88% of the effects of peptides VI and III, respectively. In spite of its high hydrophobicity, peptide IV was characterized with an abnormally low retention time when eluted from a Nucleosil C8 column during reverse-phase HPLC: it was even lower than the retention time of nonmodified peptide 562–572. However, the retention time of peptide IV, but not of other peptides, increased significantly when the eluent contained a higher proportion of trifluoroacetic acid, which disrupts micellelike structures (0.5 instead of 0.1%). The surface tension of peptide IV solution in water slightly decreased with increasing peptide concentration, but rapidly dropped and reached a plateau at the concentration of 7 × 10^–6 M, which indicates the beginning of micelle formation. Thus, peptide IV in the concentrations above 10^–5 M forms micelles, which prevents it from interacting with the receptor. The ability of GPCR peptides to aggregate and form micelles should be taken into account in the development of their new membrane-active analogs.     

Solution structure of the first and second transmembrane segments of the mitochondrial oxoglutarate carrier

The structures of the first and the second transmembrane segment of the bovine mitochondrial oxoglutarate carrier (OGC) were studied by circular dichroism (CD) and nuclear magnetic resonance (NMR) spectroscopies. Peptides 21–46 and 78–108 of its primary sequence were synthesized and structurally characterized in membrane-mimetic environments. CD data showed that at high concentrations of TFE (>50%) and SDS (>2%) both peptides assume α-helical structures, whereas in more hydrophilic environments only peptide 78–108 has a helical structure. ¹H-NMR spectra of the two peptides in TFE/water and SDS were fully assigned, and the secondary structures of the peptides were obtained from nuclear Overhauser effects, ³J_αH-NH coupling constants and αH chemical shifts. The three-dimensional solution structures of the peptides in TFE/water were generated by distance geometry calculations. A well-defined α-helix was found in the region K24-V39 of peptide 21–46 and in the region A86–F106 of peptide 78–108. We cannot exclude that in intact OGC the extension of these helices is longer. The helix of peptide 21–46 is essentially hydrophobic, whereas that of peptide 78–108 is predominantly hydrophilic.     

Differential antimitogenic effectiveness of atrial natriuretic peptides in primary versus subcultured rat aortic smooth muscle cells: Relationship to expression of ANF-C receptors

Previous studies have shown that atrial natriuretic peptides inhibit mitogenesis in subcultured aortic smooth muscle cells by a mechanism that appears to be mediated via the C-type or “clearance” receptor. In the current study, we have compared the antimitogenic effect of these peptides in serum-stimulated primary aortic smooth muscle cell cultures and in subcultured cells. A series of atrial peptides, including rANF_99–126, rANF_103–126, and rANF_103–125, were only poorly antimitogenic in serum-stimulated primary cultures, whereas des[Cys¹⁰⁵, Cys¹²¹] rANF_104–126 which binds selectively to the ANF-C receptors had no antimitogenic activity. In contrast, in subcultured cells (between subcultures 3 and 25), rANF_99–126, rANF_103–126, rANF_103–126, Cys¹¹⁶rANF_102–116, and des[Cys¹⁰⁵, Cys¹²¹]rANF_104–126 inhibited serum-induced [³H]thymidine incorporation (IC₅₀ in the range of 10–50 nM), with maximal inhibition of 40–70%. The lack of antimitogenic activity in primary cultures did not appear to be related to the lack of cGMP elevation elicited by atrial peptides or to an inherent insensitivity to the action of antimitogens, because primary cultures were responsive to the cGMP-elevating effect of atrial peptides and the cells were more rather than less sensitive to the antimitogenic effect of the nitric-oxide-vasodilator, SNAP, as compared to subcultured cells. Analysis of the affinity and binding capacity of freshly isolated aortic membranes, and primary or secondary cultures for [¹²⁵I]rANF_99–126, revealed that the number of ANF receptors increased by tenfold, following subculture. Moreover, subcultured cells contained receptors with increased binding affinity for peptide analogues selective for the ANF-C-type type receptor. Covalent cross-linking studies with (¹²⁵I)rANF_99–126 confirmed that membranes prepared from fresh aortae predominantly expressed the ANF-A/guanylate cyclase receptor, whereas in subcultured cells the predominantly cross-linked protein was the ANF-C-type receptor, with receptors in primary cultures occupying an intermediate position. These results suggest that the binding and antimitogenic activity of atrial peptides in aortic smooth muscle cells depends on the phenotypic state of these cells. Moreover, the increased antimitogenic potency of atrial peptides in secondary cultures may reflect increased expression of the ANF-C-type receptors. © 1993 Wiley-Liss, Inc.     

Synthesis and evaluation of redox-sensitive gonadotropin-releasing hormone receptor-targeting peptide conjugates

Lytic peptides have been demonstrated to exhibit obvious advantages in cancer therapy with binding ability toward tumor cells via electrostatic attractions, which are lack of active targeting and aggregation to tumor tissue. In the present study, five conjugated lytic peptides were redesigned and constructed to target gonadotropin releasing hormone receptors (GnRHr), meanwhile, the disulfide bridge was introduced to achieve redox sensitive delivery based on the experience from the preliminary work of lytic peptides P3 and P7. YX-1, was considered to be the most promising for in-depth study. YX-1 possessed high potency (IC₅₀ = 3.16 ± 0.3 μM), low hemolytic effect, and cell membrane permeability in human A2780 ovarian cancer cells. Moreover, YX-1 had prominent pro-apoptotic activity by activating the mitochondria–cytochrome c–caspase apoptotic pathway. The study yielded the conjugate YX-1 with superior properties for antineoplastic activity, which makes it a promising potential candidate for targeting cancer therapy.     

Effects of beta-endorphin and D-alanine2 enkephalinamide on urine production and urinary electrolytes in the rat.

The intracerebro-ventricular administration of human β-Endorphin (β-EP, 0.1–3 μg/rat) or D-alanine₂ methionine enkephalinamide (D-ala, 0.3–30 μg/rat) caused a dose dependent reduction in the urine volume. The oliguria was associated with a decrease in the concentration of Na⁺ and K⁺ in the urine of rats previously hydrated by oral administration with 25 ml/kg tap water plus 50 ml/kg 0.5% NaCl. On a molar basis, β-EP proved to be about 5–7 times more potent than D-ala. The effects caused by the peptides were antagonized by the simultaneous intraperitoneal administration of 1 mg/kg naloxone. In rats treated chronically with morphine, no cross-tolerance was demonstrated to the antidiuretic effect of β-EP, but clear cross-tolerance was evident to the changes in urine electrolytes induced by β-EP. Results suggest that morphine and the opiate peptides share a similar mechanism of action.     

Differential Calcitonin Gene-Related Peptide (CGRP) and Amylin Binding Sites in Nucleus Accumbens and Lung: Potential Models for Studying CGRP/Amylin Receptor Subtypes

Abstract: Calcitonin gene-related peptide (CGRP), a 37-amino-acid peptide, is a member of a small family of peptides including amylin or islet amyloid polypeptide and salmon calcitonin. These related peptides have been shown to display similar effects on in vitro and in vivo carbohydrate metabolism. The present study was initiated to identify and characterize the binding sites for these peptides in lung and nucleus accumbens membranes prepared from pig and guinea pig. Both tissues in either species displayed high-affinity (2-[¹²⁵I]iodohistidyl¹⁰)humanCGRPα ([¹²⁵I]hCGRPα) binding (IC₅₀ = 0.4–7.7 nM), which was displaced by hCGRP_8–37α with equally high affinity (IC₅₀ = 0.4–7.3 nM). High-affinity binding for [¹²⁵I]Bolton-Hunter human amylin ([¹²⁵I]BH-h-amylin) was also observed in these tissues (IC₅₀ = 0.2–6.0 nM). In membranes from the nucleus accumbens of both species, salmon calcitonin competed for amylin binding sites with high affinity (IC₅₀ = 0.1 nM) but was poor in competing for amylin binding in lung membranes. Rat amylin_8–37 competed for [¹²⁵I]hCGRPα binding with higher affinity (IC₅₀ = 5.4 nM) compared with [¹²⁵I]BH-h-amylin binding (IC₅₀ = 200 nM) in porcine nucleus accumbens, whereas in guinea pig nucleus accumbens, the IC₅₀ values for rat amylin_8–37 were 117 and 12 nM against [¹²⁵I]hCGRPα and [¹²⁵I]BH-h-amylin, respectively. Also, functional studies evaluating the activation of adenylate cyclase and generation of cyclic AMP in response to these agonists indicated that hCGRPα (EC₅₀ = 0.3 nM), h-amylin (EC₅₀ = 150 nM), and salmon calcitonin (EC₅₀ = 1,000 nM) activated adenylate cyclase, resulting in increased cyclic AMP production in porcine lung membranes that was antagonized by hCGRP_8–37α. The affinity of hCGRP_8–37α was similar for all three peptides. The cyclic AMP responses to amylin and salmon calcitonin were significantly (p < 0.05) lower than that of hCGRPα and not additive, suggesting that they are acting as partial agonists at the same CGRP1-type receptor in porcine lung membranes. Similar observations were made for guinea pig lung membranes. However, human amylin and salmon calcitonin were weaker than hCGRPα in activating lung adenylate cyclase. None of these peptides activated adenylate cyclase in membranes prepared from the nucleus accumbens of both species. The data from these studies demonstrate both species and tissue differences in the existence of distinct CGRP and amylin binding sites and present a potential opportunity to study further CGRP and amylin receptor subtypes.     

The influence of peptide impurity profiles on functional tissue-organ bath response: the 11-mer peptide INSL6[151-161] case

Bioactive peptides have great pharmaceutical potential as nutraceuticals, diagnostics, and therapeutic drugs in several clinical areas. Thus, the search for novel lead peptides with a biological function has attracted renewed interest. Crude peptide material (i.e., ～70% purity) of INSL6[151–161] (NH₂-FRSLFWGNHSQ-COOH) was found to trigger a contractile response in guinea pig ileum longitudinal smooth muscle preparations using tissue–organ baths. However, the purified peptide (i.e., ?95% purity) had no effect on this model. Further investigation with crude materials from other suppliers, with purities ranging between 50% and 80%, indicated that the crude products gave a false-positive functional tissue–organ bath conclusion. These observations question the functionality conclusions when using crude-purity peptide materials; during the initial research or discovery phase, peptide quality is generally neglected, possibly leading to misinterpretation of biological results due to by-products from peptide synthesis and, thus, wrong fail/pass decisions. Therefore, we strongly recommend appropriate quality control testing before using any peptides for initial biomedical research or discovery purposes.     

A critical comparison of the hemolytic and fungicidal activities of cationic antimicrobial peptides.

The hemolytic and fungicidal activity of a number of cationic antimicrobial peptides was investigated. Histatins and magainins were inactive against human erythrocytes and Candida albicans cells in phosphate buffered saline, but displayed strong activity against both cell types when tested in 1 mM potassium phosphate buffer supplemented with 287 mM glucose. The HC50/IC50 ratio, indicative of the therapeutic index, was about 30 for all peptides tested. PGLa was most hemolytic (HC50 = 0.6 microM) and had the lowest therapeutic index (HC50/IC50 = 0.5). Susceptibility to hemolysis was shown to increase with storage duration of the erythrocytes and also significant differences were found between blood collected from different individuals. In this report, a sensitive assay is proposed for the testing of the hemolytic activities of cationic peptides. This assay detects subtle differences between peptides and allows the comparison between the hemolytic and fungicidal potency of cationic peptides.