The cell-bound protease of Bacteroides amylophilus H18

Most of the cell-bound protease activity of Bacteroides amylophilus was attached to lysozyme spheroplasts (79%) and to the ruptured spheroplast envelope (48%). Protease activity also remained bound to mechanically ruptured cell envelopes from which it could be liberated by n-butanol treatment.Butanol-liberated protease activity was purified 80-fold, contained 23% RNA, and was excluded from G-200 Sephadex. Small molecular weight protease activity could not be liberated from this complex by treatment with acetone, EDTA, or urea. RNA could not be separated from the protease activity by treatment with streptomycin sulfate, MgCl2, or sodium dodecyl sulfate but was separated from the protein by phenol extraction. Protamine sulfate precipitation gave variable results. It is concluded that the cell-bound protease remains firmly bound to cellular components from which it cannot be liberated easily.