Purification to homogeneity of a neutral metalloproteinase from Streptomyces caespitosus

We established an improved purification procedure for Streptomyces caespitosus neutral protease (ScNP) from culture supernatants of S. caespitosus. The procedure comprises sequential ammonium sulfate fractionation and column chromatography procedures with anion exchange chromatography, followed by hydrophobic-interaction chromatography and gel filtration. Purified ScNP revealed a single band with a molecular mass of 14 kDa by SDS-PAGE under reduced conditions and did not contain any detectable pigment, which has not been completely removed by other methods. We also purified another protease with a molecular mass of 40 kDa from the culture supernatants. The pure preparation of ScNP obtained by this procedure is suitable for spectrophotometric measurement of its catalytic activity.