Proteolytic enzymes from extremely halophilic bacteria.

Halobacterium strains produce a truly extracellular proteinase which degrades gelatine and casein. It has a pH optimum of about 8 and depends upon divalent cations and a high concentration of NaCl or KC1 for activity and stability. Proteolytic enzymes were also found in cell homogenates obtained by ultra sonic treatment. A caseinolytic enzyme, probably different from the extracellular one, is associated with particles which sediment upon ultracentrifugation. A soluble peptidase of lower molecular weight is also present in the extract. Both enzymes are dependent upon divalent cations and a high concentration of NaCl or KCI for activity. In contrast to other halophilic enzymes, the proteolytic enzymes of Halobacterium sdharium are more active in the presence of NaCl than KCl at equimolar concentrations.