| Popis: |
A deoxyribonuclaese (DNase) excreted by Streptomyces rimosus to culture medium, was purified to homogeneity. Isolation procedure included fractional precipitation, gel filtration and ion exchange chromatography. Isolated DNase degraded polymerized and denatured DNA from salmon sperm, nondenatured DNA from Tenebrio molitor, circular pBR322 and pSP64 plasmid DNA, but did not hydrolyze RNA. Accordingly, the enzyme was classified as an unspecific endo-DNase. The DNase was determined to be a monomeric, basic protein with molecular mass of 21 kDa and isoelectric point approximately pH 9.5. It was stable in a broad pH range but unstable to temperature higher than 40oC. For its activity the DNase had an absolute requirement for Mg2+ or Mn2+ as its optimal pH was 8.2-8.5. For the full activity the enzyme needed free SH-groups and low ionic-strength environment. S. rimosus DNase was inhibited by EDTA, low concentration of p-chloromercuribenzoate and iodoacetamide, but was not susceptible to 2-mercaptoethanol, dithiothreitol and phenylmethylsulphonylfluoride. The sequence of 36 N-terminal amino acids was determined. It did not match the sequence of any other DNase. |
