Article (Scientific journals)
Intrinsic halotolerance of the psychrophilic alpha-amylase from Pseudoalteromonas haloplanktis
Srimathi, S.; Jayaraman, G.; Feller, Georges et al.
2007In Extremophiles: Life Under Extreme Conditions, 11 (3), p. 505-515
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Keywords :
acidic protein; Pseudoalteromonas haloplanktis alpha-amylase; halophilic; halotolerance; psychrophilic; stability
Abstract :
[en] The halotolerance of a cold adapted alpha-amylase from the psychrophilic bacterium Pseudoalteromonas haloplanktis (AHA) was investigated. AHA exhibited hydrolytic activity over a broad range of NaCl concentrations (0.01-4.5 M). AHA showed 28% increased activity in 0.5-2.0 M NaCl compared to that in 0.01 M NaCl. In contrast, the corresponding mesophilic (Bacillus amyloliquefaciens) and thermostable (B. licheniformis) alpha-amylases showed a 39 and 46% decrease in activity respectively. Even at 4.5 M NaCl, 80% of the initial activity was detected for AHA, whereas the mesophilic and thermostable enzymes were inactive. Besides an unaltered fluorescence emission and secondary structure, a 10 degrees C positive shift in the temperature optimum, a stabilization factor of > 5 for thermal inactivation and a Delta T-m of 8.3 degrees C for the secondary structure melting were estimated in 2.7 M NaCl. The higher activation energy, half-life time and T-m indicated reduced conformational dynamics and increased rigidity in the presence of higher NaCl concentrations. A comparison with the sequences of other halophilic alpha-amylases revealed that AHA also contains higher proportion of small hydrophobic residues and acidic residues resulting in a higher negative surface potential. Thus, with some compromise in cold activity, psychrophilic adaptation has also manifested halotolerance to AHA that is comparable to the halophilic enzymes.
Disciplines :
Biochemistry, biophysics & molecular biology
Author, co-author :
Srimathi, S.
Jayaraman, G.
Feller, Georges ;  Université de Liège - ULiège > Département des sciences de la vie > Labo de biochimie
Danielsson, B.
Narayanan, P. R.
Language :
English
Title :
Intrinsic halotolerance of the psychrophilic alpha-amylase from Pseudoalteromonas haloplanktis
Publication date :
May 2007
Journal title :
Extremophiles: Life Under Extreme Conditions
ISSN :
1431-0651
eISSN :
1433-4909
Publisher :
Springer, Germany
Volume :
11
Issue :
3
Pages :
505-515
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 26 January 2010

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