• Journal of Microbiology
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• v.33 no.2
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• pp.103-108
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• 1995

Streptomyces fradiae protease inhibitor (SFI) was purified effectively by preparative isoelectric focusing and hydroxyapatite chromatography. The molecular weight of SFI was estimated to be 1.7 kDa by SDS-PAGE and 1.8 kDa by molecular sieving HPLC. One hundred and sixty amino acid residues were determined from which molecular weight of SFI was calculated to be 17.054 Da and carbohydrate residue was not detected. SFI was calculated to be 17,064 Da and carbohydrate residue was not detected. SFI was a monomeric protein with two reactive sits, of which isoelectric point was pH 4.1. N-terminal amino acid sequence of SFI had homology with SSI (Streptomyces subsilisin inhibitor) and other protease inhibitors produced by Streptomyces.