Human neutrophil elastase (HNElastase, EC 3.4.21.37), a causative factor of inflammatory diseases, was purified by Ultrogel AcA54 gel filtration and CM-Sephadex ion exchange chromatography. HNElastase was inhibited by phenylbutazone in a concentration dependent manner up to 0.4 mm, but as the concentration increased, the inhibitory effect gradually diminished. Binding of phenylbutazone to the human neutrophil elastase caused strong Raman shifts at 200, 440, and 1194 cm-1. The peak at 1194 cm-1 might be evidence of the presence of -N=N-PHI radical. The core area of the elastase, according to the visual molecular model of human neutrophil elastase, was structurally stable. A deeply situated active center was at the core area surrounded by hydrophobic amino acids. Directly neighboring the active site was one positively charged atom and two atoms carrying a negative charge, which enabled the enzyme and the drug to form a strong interaction. Phenylbutazone may form a binding, similar to a key & lock system to the atoms carrying opposite charges near the active site of the enzyme molecule. Furthermore, the hydrophobicity of the surrounding amino acid near the active site seemed to enhance the binding strength of phenylbutazone. Binding of phenylbutazone near the active site may cause masking of the active site, preventing the substrate from approaching the active site and inhibiting elastase activity.
Amino Acids ; Catalytic Domain ; Chromatography, Gel ; Chromatography, Ion Exchange ; Humans* ; Hydrophobic and Hydrophilic Interactions ; Leukocyte Elastase* ; Masks ; Models, Molecular ; Neutrophils* ; Pancreatic Elastase ; Phenylbutazone*

Nonsteroidal antiinflammatory drugs(NSAIDs) are known as clinically effective agents for treatment of inflammatory diseases. Inhibition of cyclooxygenase has been thought to be a major facet of the pharmacological mechanism of NSAIDs. However, it is difficult to ascribe the antiinflammatory effects of NSAIDs solely to the inhibition of prostaglandin synthesis. Human neutrophil elastase (HNElastase; HNE, EC 3.4.21.37) has been known as a causative factor in inflammatory diseases. To investigate the specific relationship between HNElastase inhibition and specificity of molecular structure of several NSAIDs, HNElastase was purified by Ultrogel AcA54 gel filtration, CM-Sephadex ion exchange, and HPLC (with TSK 250 column) chromatography. HNElastase was inhibited by aspirin and salicylate in a competitive manner and by naproxen, ketoprofen, phenylbutazone, and oxyphenbutazone in a partial competative manner, but not by ibuprofen and tolmetin. HNElastase-phenylbutazone-complex showed strong Raman shifts at 200, 440, 1124, 1194, 1384, 1506, and 1768 cm(-1). The Raman bands 1194, 1384, and 1768 cm(-1) may represent evidences of the conformational change at -N=N-phi radical, pyrazol ring, and -C=O radical of the elastase-drug complex, respectively. Phenylbutazone might be bound to HNElastase by ionic and hydrophobic interaction, and masked the active site. Inhibition of HNElastase could be another mechanism of action of NSAIDs besides cyclooxygenase inhibition in the treatment of inflammatory diseases. Different inhibition characteristics of HNE-lastase by NSAIDs such as aspirin, phenylbutazone-like drugs and ineffective drugs could be important points for drawing the criteria for appropriate drugs in clinical application.
Anti-Inflammatory Agents, Non-Steroidal/pharmacology* ; Chromatography, Affinity ; Computer Simulation ; Enzyme Inhibitors/pharmacology ; Human ; Isoenzymes/isolation & purification ; Isoenzymes/antagonists & inhibitors ; Ketoprofen/pharmacology ; Leukocyte Elastase/isolation & purification ; Leukocyte Elastase/antagonists & inhibitors* ; Models, Molecular ; Naproxen/pharmacology ; Phenylbutazone/analogs & derivatives ; Salicylates/pharmacology ; Spectrum Analysis, Raman