title: Effect of nutritional conditions on extracellular protease production by the haloalkaliphilic archaeon Natrialba magadii.
abstract: OBJECTIVE
  The effect of various nitrogen sources and nutritional starvation was examined on the production of an extracellular protease secreted by the haloalkaliphilic archaeon Natrialba magadii.
  
  
  RESULTS
  Cell growth and proteolytic activity were measured in cells grown with different nitrogen sources. Proteolytic activity was produced in complex and easily metabolized nitrogen sources such as yeast extract, casein and casamino acids; meanwhile, ammonium repressed enzyme production. The time course and amount of protease accumulated showed an inverse correlation with growth rate and nutrient concentration. Starvation did not induce extracellular protease production.
  
  
  CONCLUSIONS
  The accumulation of Nab. magadii extracellular protease is stimulated by nutrient limitation and slow growth rate indicating that it is probably induced in response to a deficit in the energetic status of the cells. Nutritional starvation did not induce protease accumulation suggesting that de novo synthesis of this protease and/or factor/s necessary for its activation are required. This enzyme may be regulated by nitrogen catabolite repression and it does not require protein substrates for induction.
  
  
  CONCLUSIONS
  These results contribute to the basic knowledge on protease regulation in haloalkaliphilic archaea and will help to optimize the production of this extremozyme for biotechnological applications such as protease-catalysed peptide synthesis.
authors.affiliation: Instituto de Investigaciones Biológicas, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina.
authors.forename: C P
authors.initials: CP
authors.lastname: D'Alessandro
authors.forename: R E
authors.initials: RE
authors.lastname: De Castro
authors.forename: M I
authors.initials: MI
authors.lastname: Giménez
authors.forename: R A
authors.initials: RA
authors.lastname: Paggi
mesh_terms: D019843:Archaeal Proteins / Q000032:analysis / Q000096:biosynthesis*; D018929:Cell Culture Techniques; D003470:Culture Media / Q000737:chemistry / Q000494:pharmacology; D006216:Halobacteriaceae / Q000187:drug effects* / Q000201:enzymology* / Q000254:growth & development; D009584:Nitrogen / Q000032:analysis / Q000494:pharmacology*; D010447:Peptide Hydrolases / Q000032:analysis / Q000096:biosynthesis*; D015003:Yeasts / Q000737:chemistry
chemical_list: D019843:Archaeal Proteins; D003470:Culture Media; D010447:Peptide Hydrolases; D009584:Nitrogen