FR901277, a novel inhibitor of human leukocyte elastase from Streptomyces resistomycificus. Producing organism, fermentation, isolation, physico-chemical and biological properties

Peptide Human Neutrophil Elastase Inhibitors from Natural Sources: An Overview

Elastases are a broad group of enzymes involved in the lysis of elastin, the main component of elastic fibres. They are produced and released in the human body, mainly by neutrophils and the pancreas. The imbalance between elastase activity and its endogenous inhibitors can cause different illnesses due to their excessive activity. The main aim of this review is to provide an overview of the latest advancements on the identification, structures and mechanisms of action of peptide human neutrophil elastase inhibitors isolated from natural sources, such as plants, animals, fungi, bacteria and sponges. The discovery of new elastase inhibitors could have a great impact on the pharmaceutical development of novel drugs through the optimization of the natural lead compounds. Bacteria produce mainly cyclic peptides, while animals provide for long and linear amino acid sequences. Despite their diverse natural sources, these elastase inhibitors show remarkable IC₅₀ values in a range from nM to μM values, thus representing an interesting starting point for the further development of potent bioactive compounds on human elastase enzymes.

Dinghupeptins A-D, Chymotrypsin Inhibitory Cyclodepsipeptides Produced by a Soil-Derived Streptomyces

Four new cyclodepsipeptides, dinghupeptins A-D (1-4), possessing a rare N⁵-(2-hydroxylethyl)glutamine moiety, were isolated from cultures of the soil-derived Streptomyces sp. SC0581. Their structures were elucidated by spectroscopic and advanced Marfey's amino acid analysis, and their 3D structures were established by theoretical conformational analysis. Compounds 1 and 2, containing a 3-amino-6-hydroxypiperidone unit, displayed selective inhibition of chymotrypsin with IC₅₀ values of 2.1 and 1.1 μM, respectively. Enzyme kinetic analysis and molecular docking experiments revealed they are competitive inhibitors binding to the active site of chymotrypsin.

Resisting degradation by human elastase: commonality of design features shared by 'canonical' plant and bacterial macrocyclic protease inhibitor scaffolds

A previously unexplained difference in the resistance to enzymatic hydrolysis of 11-mer Bowman-Birk-type inhibitors of human leukocyte elastase that differ in P1 is found to correlate with the strength of a particular intramolecular hydrogen bond within the inhibitor. This transannular hydrogen bond stabilizes the side chain of the conserved P2 Thr in a 'canonical' +60 degrees -rotamer chi(1) conformation and thereby directs it for a close interaction with the enzyme's catalytic His. As the implications of this NMR analysis are neither limited to this macrocyclic scaffold derived from plant proteins nor to a particular serine protease, we present a unified analysis with inhibitory bacterial depsipeptides of 7-12 residues in length that share key design features for which we propose communal functional explanations.

Structure of porcine pancreatic elastase complexed with FR901277, a novel macrocyclic inhibitor of elastases, at 1.6 A resolution

Human leukocyte elastase (HLE) is a serine protease that contributes to tissue destruction in various disease states-for example, in emphysema. FR901277 is a natural product isolated from the culture filtrate of Streptomyces resistomicificus and is a potent inhibitor of both HLE and porcine pancreatic elastase (PPE). FR901277 consists of four normal amino acids and three unusual amino acids, and is a unique bicyclic peptide compound. The crystal structure of PPE complexed with FR901277 has been determined at 1.6 A resolution. The Ogamma atom of Ser-195 in PPE did not form a covalent bond with FR901277, but formed a hydrogen bond with the Nvarepsilon atom of His-57. On the other hand, the portion from L-Orn(1) through dehydroxyThr(3) in FR901277 formed an antiparallel beta-sheet structure with the backbone of the active site in PPE. The S4 through S2' binding subsites in PPE were all occupied by the hydrophobic side chains of the inhibitor molecule. Especially, the ethylidene moiety of FR901277 occupied the S1 specific pocket, indicating a CH/pi interaction. In addition, the isopropyl side chain of L-Val(7) was located at the enzyme surface between the S2 and S1' pockets with several van der Waals contacts. However, the amino acid (4) residue was not involved in a significant interaction with PPE. Comparison of inhibitor structures in different environments showed that FR901277 has a highly rigid bicyclic framework; however, it can slightly change its conformation according to the circumstances. The binding mode of FR901277 at the active site of PPE was directly applicable to that in HLE, after consideration of induced fit. The structure of the PPE-FR901277 complex provided much information regarding potential sites for modification of the physicochemical properties of FR901277.

1H-NMR determination of the solution structure and absolute configuration of FR134043, a novel inhibitor of human leukocyte elastase

FR134043 is a semisynthetic disulfonated derivative of the natural product FR901277, is isolated from the culture filtrate of Streptomyces resistomicificus and has potent inhibitory activity against human leukocyte elastase. Although the chemical structure of FR134043 was determined to be a unique bicyclic peptide-like compound consisting of seven amino acids by using several spectroscopic analytical methods, the chiralities of three centers were unknown. A simple simulated annealing protocol to determine the structure was applied to the eight possible stereoisomers, and the one that best satisfied the NOE distance constraints was determined to be the true stereoconfiguration of FR134043. The solution structure showed that all Calpha atoms existed in the L configuration and six of the seven side chains were located towards the outside of the bicyclic framework, even though most of them are highly hydrophobic moieties. The simulated annealing calculation described here is a frequently used method for the determination of the solution structure of peptides or small proteins. We show here that it is also applicable to the determination of the absolute configuration of macrocyclic compounds produced from natural sources.

Molecular structure of FR901277, a novel inhibitor of human leukocyte elastase, and its binding mode simulation

X-ray crystal structure analysis of FR901277, a novel inhibitor of human leukocyte elastase, was performed and revealed that the lipophilic side chains are located towards the outside of the molecule. Binding simulation using computational methods showed that these lipophilic moieties could bind to the hydrophobic binding pockets of HLE.

Release of neutrophil elastase and its role in tissue injury in acute inflammation: effect of the elastase inhibitor, FR134043

Neutrophil elastase degrades extracellular matrix components and is involved in tissue destruction in several inflammatory states. We examined the inhibition of the elastase activity derived from activated neutrophils in vitro and in vivo by FR134043, disodium-(Z,1S,15S,18S,24S,27R,29S,34S,37R)-29-b enzyl-21-ethylidene-27-hydroxy-15-isobutyrylamino-34-isopropyl-31, 37-dimethyl-10,16,19,22,30,32,35,38-octaoxo-36-oxa-9,11,17,20,23,2 8,31,33-octaazatetracyclo[16.13.6.1(24,28).0(3,8)]octatriconta+ ++-3,5,7-trien-5,6-diyl disulfate, an elastase inhibitor with broad specificity, and elucidated the role of neutrophil elastase in pathogenesis of acute inflammation. In a culture of human neutrophils, phorbol myristate acetate (PMA) and calcium ionophore increased elastase activity in the supernatants, which was amplified by co-existing mononuclear leukocytes. Formyl-Met-Leu-Phe stimulated elastase release in the presence of, not without, mononuclear leukocytes. Intratracheal injection of lipopolysaccharide elevated the elastase activity in bronchoalveolar lavage fluid of rats. These elastase activities were significantly inhibited by FR134043. Intratracheal treatment with FR134043 in rats also inhibited the enzyme induced by lipopolysaccharide, though the maximum inhibition was 52%. Ear edema elicited by topical application of PMA in mice was significantly suppressed by pretreatment with FR134043 (38% inhibition at 1 mg/ear). In carrageenan-induced joint injury in rats, plasma extravasation into the synovial cavity was partially and significantly inhibited by FR134043 at 1 mg/knee, while an elastase-specific inhibitor showed no effect. These results suggest that neutrophil elastase is partially involved in tissue damage in acute inflammation provoked by irritants, but not in carrageenan-induced hyperpermeability.

Hepatic clearance of ONO-5046, a novel neutrophil elastase inhibitor, in rats and in the rat perfused liver

The hepatic clearance of ONO-5046 (N-[2-[4-(2,2-dimethylpropionyloxy)phenylsulphonylamino]benz oyl]aminoacetic acid), a low-molecular-weight neutrophil elastase inhibitor, has been investigated in rats and in the rat perfused liver. This ester was easily hydrolysed to its inactive metabolite EI-601 (N-[2-[(4-hydroxyphenyl)sulphonylamino]benzoyl]aminoacetic acid) in liver homogenate and in erythrocytes suspension in-vitro. On the other hand, it was stable in biological media such as plasma and whole blood, which contain plasma proteins. Scatchard plot analysis of ONO-5046 binding to bovine serum albumin (BSA) in-vitro indicated that the association constant (K) and number of binding sites (n) were 6.91 x 10(4) (M(-1)) and 4.33, respectively. Thus, ONO-5046 (100 microM) would bind to plasma proteins to an extent >99% at physiological plasma-protein concentrations. The total plasma clearance of ONO-5046 in rats was constant (approximately 9 mL min(-1) kg(-1)) under different steady-state plasma concentrations (5-50 microM) a value equivalent to the hepatic clearance. In the rat perfused liver, the hepatic extraction ratio of ONO-5046 was significantly reduced by adding BSA to the dosing solution. Thus, the relatively low hepatic clearance of ONO-5046, which has an ester linkage in its structure and is naturally susceptible to enzymatic hydrolysis, was found to be because of the extremely high protein-binding of the compound.

Biochemical and pharmacological characterization of FR134043, a novel elastase inhibitor

FR134043, disodium(Z,1S,15S,8S,24S,27R,29S,34S,37R)-29-ben zyl-21-ethylidene-27-hydroxy-15-isobutyrylamino-34-isopropyl-31,37 -dimethyl-10,16,19,22,30,32,35,38-octaoxo-36-oxa-9,11,17,20,23,28, 31,33-octaazatetracyclo[16.13.6.1(24),(28).0(3),(8)]octatricont a-3,5,7-trien-5,6-diyl disulfate, is a water-soluble inhibitor of human neutrophil elastase with a molecular mass of 1166.15 Da. FR134043 demonstrated a characteristic competitive inhibition of human neutrophil elastase with a Ki of 8 nM. In studies using synthetic substrates, FR134043 inhibited both neutrophil elastase activity and porcine pancreatic elastase activity with IC50 values of 35 nM and 49 nM respectively. FR134043 also inhibited hydrolysis of bovine neck ligament elastin by human neutrophil elastase with an IC50 value of 210 nM. In in vivo experiments, FR134043 protected animals against human neutrophil elastase (50 microg/animal)-induced lung hemorrhage in hamsters with an ED50 value of 3.1 microg/animal for intratracheal administration and 5.0 mg/kg for intravenous administration. Subcutaneous treatment with FR134043 significantly suppressed human neutrophil elastase (20 microg/paw)-induced paw edema in mice with an ED50 value of 3.3 mg/kg when evaluated 4 h after elastase injection. The potency of FR134043 given intratracheally to protect against porcine pancreatic elastase (100 microg/animal)-induced emphysema in hamsters was relatively low (Quasi-static lung compliance; ED50 = 1590 microg/animal) compared to that in acute animal models. FR134043 (10 mg/kg per h i.v. infusion) significantly improved lipopolysaccharide (0.25 mg/kg per h i.v. infusion)-induced thrombocytopenia and some coagulation parameters in rats. These results suggest that systemic administration of FR134043 would be advantageous over intratracheal administration of FR134043 for the treatment of adult respiratory distress syndrome, septic shock and pulmonary emphysema and other pathophysiologic conditions in which elastases are thought to be involved.

Novel screen methodologies for identification of new microbial metabolites with pharmacological activity

Micro-organisms continue to provide an important source of chemical diversity for the discovery of compounds with new biological activities. Microbial metabolites discovered recently using assays to detect compounds with potential pharmacological utility are surveyed and found to represent an extensive range of structural types produced by a wide variety of organisms. Assays used for screening samples produced by microbial processes must be robust, sensitive and specific and able to operate above a background of potential interferences from a number of sources. Discovery assays currently in use fall into three main categories cell-based, receptor-ligand interaction and enzyme inhibition assays. Trends in the use of these assays and new developments in assay technology applicable to the screening of microbial samples are examined with particular reference to the high throughput screening environment. For microbial screening to be a competitive route to new drug leads, the disciplines involved must be engineered into a seamlessly integrated process to deliver novel compounds with the required biological properties rapidly.