PURIFICATION AND PROPERTIES OF A PROTEINACEOUS METALLO-PROTEINASE INHIBITOR FROM STREPTOMYCES-NIGRESCENS TK-23

A novel metallo-proteinase inhibitor which is capable of inhibiting the activities of metallo-proteinases such as thermolysin, was isolated from the culture filtrates of Streptomyces nigrescens TK-23. The inhibitor was purified batch-wise from the culture filtrate by Amberlite IRC-50 and column chromatographies on CM-Sephadex C-50 and Sephadex G-50. The purified inhibitor showed a single band on 15% polyacrylamide gel electrophoresis at pH 4.3, and at pH 7.5 on SDS-gels. The inhibitor retained 80% of its original activity after treatment of 100°C for 5 min between pH 2 and 7. The molecular weight was estimated to be 12 000 by gel filtration and SDS-polyacrylamide gel electrophoresis, and calculated as 11 950 from its amino acid composition. The isoelectric point was pH 10.3. The inhibitor showed a high content of hydrophobic amino acids, did not contain tryptophan, and had two disulfide bridges. It also showed specific inhibitory activity for metallo-proteinases but not for serine-, thiol- and carboxyl-proteinases. © 1979.