title: Catalytic and thermodynamic characterization of protease from Halobacterium sp. SP1(1).
abstract: Osmolytes KCl, glycerol, mannitol, trehalose, sucrose, betaine, proline and Na-glutamate at different concentrations (5-30%) were investigated as effective solutes for retaining the activity of Halobacterium sp. SP1(1) protease in the absence of NaCl. Maximum activity was observed in the presence of 30% Na-glutamate. Kinetic and thermodynamic parameters for casein hydrolysis revealed that the protease was equally efficient in the presence of Na-glutamate as in NaCl. The enzyme was active over a broader range of temperature (20-80 degrees C) and was highly stable even at 80 degrees C with Na-glutamate. Thermodynamic parameters (DeltaH*, DeltaS*, G*) for irreversible inactivation of protease at different temperatures (20-80 degrees C) were determined in the presence of Na-glutamate and NaCl. The efficiency of these osmolytes for thermal stability of protease was 30% (1.6 M) Na-glutamate > 4 M ( approximately 25%) NaCl > 2 M (approximately 10%), suggesting that the effect exerted by the osmolyte depends not only on its chemical nature but also on its concentration. Na-glutamate was thus found to play an important role in thermal stabilization of enzyme substituting for NaCl. Moreover, substitution of NaCl by Na-glutamate may increase the applicability of halophilic enzymes in biotechnology and industry, which is otherwise limited to high NaCl concentrations.
authors.affiliation: Department of Microbiology and Biotechnology Centre, Faculty of Science, The Maharaja Sayajirao University of Baroda, Vadodara 390002, India.
authors.forename: Aparna V
authors.initials: AV
authors.lastname: Akolkar
authors.forename: Anjana J
authors.initials: AJ
authors.lastname: Desai
mesh_terms: D019843:Archaeal Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D055162:Biocatalysis; D002364:Caseins / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004795:Enzyme Stability; D006217:Halobacterium / Q000201:enzymology*; D006358:Hot Temperature; D006868:Hydrolysis; D009994:Osmolar Concentration; D010447:Peptide Hydrolases / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*; D012965:Sodium Chloride / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D019843:Archaeal Proteins; D002364:Caseins; D004791:Enzyme Inhibitors; D012965:Sodium Chloride; D010447:Peptide Hydrolases