Purification and biochemical characterization of the haloalkaliphilic archaeon Natronococcus occultus extracellular serine protease.

STUDDERT C.A., HERRERA SEITZ MK, PLASENCIA GIL M.I., SÁNCHEZ J.J AND DE CASTRO, R E.

JOURNAL OF BASIC MICROBIOLOGY

Año: 2001 vol. 41 p. 375 - 383

0233-111X

A serine protease was purified from Natronococcus occultus stationary phase culture medium (328-fold,yield 19%) and characterized at the biochemical level. The enzyme has a native molecular mass of 130kDa, has chymotrypsin-like activity, is stable and active in a broad pH range (5.5-12), is rather thermophilic (optimal activity at 60 °C in 1-2 M NaCl) and is dependent on high salt concentrations for activity and stability (1-2 NaCl or KCl). Polyclonal antibodies were raised against the purified protease. In Western blots, they presented no cross-reactivity with culture medium from other halobacteria nor with commercial proteases except subtilisin. The amino acid sequences of three tryptic peptides obtained from Natronococcus occultus protease did not show significant similarity to other known proteolytic enzymes. This fact, in addition to its high molecular mass suggests that Natronococcus occultus extracellular protease may be a novel enzyme.