Regina Kasprzykowska

Cystatin C Based Peptidyl Diazomethanes as Cysteine Proteinase Inhibitors: Influence of the Peptidyl Chain Length

The peptidyl diazomethanes Cbz-Gly-CHN2, Boc-Val-Gly-CHN2, H-Leu-Val-Gly-CHN2, Cbz-Leu-Val-Gly-CHN2 and Cbz-Arg-Leu-Val-Gly-CHN2, with peptidyl portions modelled after the proposed cysteine proteinase interacting N-terminal segment of human cystatin C, were synthesized. Their efficiency as cysteine proteinase inhibitors was tested against papain, human cathepsin B and bovine cathepsin B. All, except Cbz-Gly-CHN2, were found to be irreversible inhibitors of the tested enzymes. Each addition of an amino acid residue to their peptidyl portions resulted in an increased inhibition rate of all three enzymes. These data suggest that the arginyl residue of the tetrapeptidyl diazomethane, and also the corresponding arginyl residue in native cystatin C, interact with a S4 substrate pocket subsite of both papain and cathepsin B. The most efficient inhibitor, Cbz-Arg-Leu-Val-Gly-CHN2, inhibited papain and cathepsin B with rate constants of the same order of magnitude as those for L-3-carboxy-trans-2,3-epoxypropionyl-leucylamido-(4-guanidin o)butane (E-64). The high water-solubility of Cbz-Arg-Leu-Val-Gly-CHN2 allowing it to be dissolved to molar concentrations without use of non-physiological additives, makes it suitable for in vitro and in vivo cysteine proteinase inhibition studies.

Synthesis of cysteine proteinase inhibitors structurally based on the proteinase interacting N-terminal region of human cystatin C.

Fibronectin contains two latent gelatinolytic enzymes, FN-gelatinase and FN-laminase that can be activated in the presence of Ca2+ from the purified cathepsin D-produced 190-kDa fibronectin fragment. The results of this work show that Achromobacter collagenase cleaves fibronectin and generates an active FN-gelatinase. In contrast to the cathepsin D digest, the collagenase digest directly exhibits gelatinolytic activity without additional activation. The gelatinolytic activity of the total collagenase digest can be inhibited by phenylmethanesulfonyl fluoride, a serine proteinase inhibitor and by pepstatin A, an aspartic-acid proteinase inhibitor. FN-laminase activity, when assayed with its synthetic substrate GPAGPR and also with laminin was revealed after separation of the collagenase digest of fibronectin on heparin Ultrogel. FN-gelatinase and FN-laminase activities were found in heparin unretained and heparin strongly retained fractions. These results have demonstrated that in contrast to cathepsin D, Achromobacter collagenase activates two matrix-degrading proteinases from fibronectin, FN-Gelatinase und FN-Laminase.

A peptidyl derivative structurally based on the inhibitory center of cystatin C inhibits bone resorption in vitro

Human cystatin C is a cysteine proteinase inhibitor belonging to the cystatin superfamily, which previously has been shown to inhibit bone resorption in bone organ culture. The aminoterminal segment, Arg(8)-Leu(9)-Val(10)-Gly(11) (RLVG), of the single polypeptide chain of cystatin C constitutes an essential part of its inhibitory center. In the present study, the effect of benzyloxycarbonyl-Arg(8)-Leu(9)-Val(10)-Gly(11)-diazomethane (Z-RLVG-CHN(2)) on bone resorption in vitro was compared with the effects of cystatin C and calcitonin. Bone resorption was assessed by the release of (45)Ca and (3)H from mouse calvarial bones prelabeled with [(45)Ca]CaCl(2) and [(3)H]-proline, respectively. Z-RLVG-CHN(2) concentration-dependently inhibited the release of (45)Ca and (3)H in bones stimulated by parathyroid hormone (PTH), with half-maximal inhibition obtained at 1 micromol/L. The inhibitory actions of Z-RLVG-CHN(2) and cystatin C were persistent, whereas action induced initially by calcitonin was lost with time. The inhibition caused by Z-RLVG-CHN(2) and cystatin C on PTH-stimulated (45)Ca release was observed after 6 h, whereas inhibition by calcitonin was seen already after 2 h. In contrast, the inhibitory effects of Z-RLVG-CHN(2) and cystatin C, as well as that of calcitonin, on (3)H release was seen already after 2 h. Z-RLVG-CHN(2), in which the reactive carboxyterminal diazomethane was substituted by nonreactive groups [-OH, -NH(2), or -N(CH(3))(2)], resulted in peptidyl derivatives, which, in contrast to Z-RLVG-CHN(2) and cystatin C, inhibited neither cysteine proteinases nor bone resorption. In contrast to wild-type cystatin C, recombinant human cystatin C with Gly substitutions for residues Arg(8), Leu(9), Val(10), and Trp(106), and with low or nonexistent affinity for cysteine proteinases, did not display any inhibitory effect on bone resorption. These data strongly indicate that Z-RLVG-CHN(2) inhibits bone resorption in vitro by a mechanism that seems primarily to be due to an inhibition of bone matrix degradation via cysteine proteinases. The data also corroborate the hypothesis that cystatin C inhibits bone resorption by virtue of its cysteine proteinase inhibitory capacity.

New antimicrobial cystatin C-based peptide active against gram-positive bacterial pathogens, including methicillin-resistant Staphylococcus aureus and multiresistant coagulase-negative staphylococci.

We describe the synthesis and antibacterial properties of a novel antimicrobial peptidyl derivative, (2S)‐2‐(Nα‐benzyloxycarbonyl‐arginyl‐leucylamido‐1‐[(E)‐cinnamoylamido]‐3‐methylbutane, structurally based upon the inhibitory centre of the human cysteine protease inhibitor, cystatin C. The derivative, here called Cystapep 1, displayed antibacterial activity against several clinically important gram‐positive bacteria. It displayed minimal inhibitory and bactericidal concentrations of about 16 μg/ml for both Staphylococcus aureus and Streptococcus pyogenes. In radial agar diffusion assays, groups A, B, C and G streptococci as well as staphylococci were generally susceptible to the action of Cystapep 1, whereas pneumococci and enterococci were less susceptible. No activity against gram‐negative bacteria was observed. Cystapep 1 also showed high activity against methicillin‐resistant S. aureus (MRSA) and multiantibiotic‐resistant coagulase‐negative staphylococci (CNS), suggesting that its mechanism of action differs from those of most currently used antibiotics.

Synthesis and antibacterial properties of peptidyl derivatives and cyclopeptides structurally based upon the inhibitory centre of human cystatin C: Dissociation of antiproteolytic and antibacterial effects

Cysteine protease‐inhibiting proteins of the cystatin superfamily can inhibit the replication of certain viruses and bacteria. The inhibitory centre of human cystatin C, the most widely distributed human cystatin, comprises three peptide segments. The present work describes the synthesis and antibacterial activity of 27 new peptidyl derivatives or cyclopeptides based upon the aminoterminal segment Arg8‐Leu9‐Val10‐Gly11. Fourteen of the new compounds displayed antibacterial activity against from 1 up to 9 of 17 clinically important bacterial species tested. Antiproteolytic activity of a compound was usually not required for its antibacterial capacity. Peptidyl diazomethanes generally had a very narrow antibacterial spectrum, inhibiting only Streptococcus pyogenes, whereas cyclopeptides and peptidyl derivatives of the general structure X‐Arg‐Leu‐NH‐CH(iPr)‐CH2‐NH‐Y had a much wider spectrum. The most potent of these substances displayed approximately equal minimal inhibitory and bactericidal concentrations of about 20 μg/ml for both Staphylococcus aureus and S. pyogenes and were devoid of antiproteolytic activity. Several of the new substances could protect mice against lethal intraperitoneal challenge with S. pyogenes. Though their target remains to be disclosed, the group of substances here reported might be promising for the development of antibacterial drugs and the discovery of novel principles of action.

Simple and efficient synthesis of chiral amino alcohols with an amino acid-based skeleton

Sodium bis(2-methoxyethoxy)aluminum hydride, NaAlH2(OCH2CH2OCH3)2, commercially known as Vitride® or Red-Al®, enables rapid synthesis of pure optically active N-protected amino alcohols and peptide alcohols in very high yields. The method is very simple and attractive, as it does not require an additional step of N-protected amino acid derivatization and proceeds without the loss of enantiomeric homogeneity.

Acid-catalyzed isomerization of methyl 2-deoxy-D-arabino-hexosides: equilibria, kinetics and mechanism.

Four isomers of methyl 2-deoxy-D-arabino-hexosides were isolated by HPLC as chromatographically homogeneous compounds. The rates of pyranoside isomerization (alpha(p) and beta(p)) at 40 degrees C and of furanoside isomerization (alpha(f) and beta(f)) at 26 degrees C were determined. A mechanism has been suggested for transformations taking place during isomerization of methyl 2-deoxy-D-arabino-hexosides in methanolic solution catalyzed with hydrogen chloride.

Computer modeling of the solution conformation of cyclic enkephalins

The probable conformations of two cyclic enkephalin analogs, DNS-cyclo[d-Dab-Gly-Trp-Leu] (I) and DNS-cyclo[d-Dab-Gly-Trp-d-Leu] (II) (DNS=dansyl), were determined by combining the results of NOE, vicinal coupling constant and fluorescence energy transfer measurements with theoretical calculations. The common feature of the conformations for both peptides is the presence of a β-turn at residues 2 and 3.

Search of synthetic low-molecular peptide derivatives with activity against fungal pathogens

Venomous animals have evolved a vast array of peptide toxins for prey capture and defence. These peptides are highly prospective for rapid drug discovery as they are active towards a wide variety of pharmacological targets such as ion channels or G-protein coupled receptors (GPCRs) in the nervous system. Here we describe Xenomes drug development process for the chi family, conopeptide _-MrIA[1] of the predatory marine snail Conus marmoreus, leading to a suitable drug candidate (Xen2174). Xen2174 is highly selective for the norepinephrine transporter (NET) compared to other transporters, such as dopamine and serotonin, and inhibits NET via an allosteric mechanism. Xen2174 is currently in a phase I/IIa clinical trial for the treatment of severe pain. An intensive synthetic analogue and screening program around _-MrIA, incorporating early stage animal data, resulted in the identification of Xen2174, a drug with improved plasma stability, linear pharmacokinetics and wide therapeutic window. Xen2174 isomers were synthesized via selective disulfide bond formation to identify the active connectivity. Data from alanine- scans, single amino acid mutations and probing of backbone interactions combined with the full 3D NMR structure, led to the development of a pharmacophore for Xen2174. This model is refined from further studies where STRUCTURE-ACTIVITY RELATIONSHIPs were developed utilising binding and functional assay data for a range of peptides.