Characterization and identification of partial amino acid sequence of a novel elastase inhibitor, Asnidin from Aspergillus nidulans.

A novel elastase inhibitor from Aspergillus nidulans NBRC 4340, Asnidin, was isolated, and biochemical properties and partial amino acid sequence were examined. Column chromatography using diethylaminoethyl (DE) 52-Cellulose and reversed-phase HPLC were used to purify the inhibitor. Purified Asnidin was found to be homogeneous as indicated by reversed-phase HPLC and TOF-MS (Time of Flight Mass Spectrometry). Asnidin has a molecular weight of 4,181.63 as determined by TOF-MS. The elastolytic activities of elastases from A. fumigatus, A. flavus, and human leukocytes but not chymotrypsin, and elastases from snake venom and bacteria were inhibited by Asnidin. The fibrinogenase and collagen type IV hydrolytic activities of the elastase from A. fumigatus were inhibited by Asnidin. Asnidin was found to be stable under heat treatment and over a wide pH range. The elastolytic inhibitory activity of Asnidin was inhibited by dithiothreitol (DTT), while no inhibition was observed with ethylenediaminetetraacetic acid (EDTA-2Na) and benzamidine. Since there is a possibility of Asnidin becoming another drug in the arsenal of weapons against aspergillosis or interstitial pneumonia, further studies are warranted.