Extremophiles

, Volume 11, Issue 3, pp 505–515

Intrinsic halotolerance of the psychrophilic α-amylase from Pseudoalteromonas haloplanktis

  • Soundararajan Srimathi
  • Gurunathan Jayaraman
  • Georges Feller
  • Bengt Danielsson
  • Paranji R. Narayanan
Original Paper

DOI: 10.1007/s00792-007-0062-5

Cite this article as:
Srimathi, S., Jayaraman, G., Feller, G. et al. Extremophiles (2007) 11: 505. doi:10.1007/s00792-007-0062-5

Abstract

The halotolerance of a cold adapted α-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) α-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°C positive shift in the temperature optimum, a stabilization factor of >5 for thermal inactivation and a ΔTm of 8.3°C for the secondary structure melting were estimated in 2.7 M NaCl. The higher activation energy, half-life time and Tm indicated reduced conformational dynamics and increased rigidity in the presence of higher NaCl concentrations. A comparison with the sequences of other halophilic α-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.

Keywords

Acidic proteinPseudoalteromonas haloplanktis α-amylaseHalophilicHalotolerancePsychrophilicStability

Abbreviations

AHA

Pseudoalteromonas haloplanktis α-amylase

PPA

Porcine pancreatic α-amylase

BAA

Bacillus amyloliquefaciens α-amylase

BLA

Bacillus licheniformis α-amylase

Supplementary material

Copyright information

© Springer 2007

Authors and Affiliations

  • Soundararajan Srimathi
    • 1
    • 2
    • 4
  • Gurunathan Jayaraman
    • 2
    • 5
  • Georges Feller
    • 3
  • Bengt Danielsson
    • 4
  • Paranji R. Narayanan
    • 1
  1. 1.Department of MicrobiologyTuberculosis Research CentreChennaiIndia
  2. 2.Centre for Protein Engineering and Biomedical ResearchThe Voluntary Health ServicesChennaiIndia
  3. 3.Laboratory of Biochemistry, Institute of ChemistryUniversity of LiègeLiègeBelgium
  4. 4.Pure and Applied BiochemistryLund UniversityLundSweden
  5. 5.Biotechnology Unit, School of Biotechnology and Chemical EngineeringVellore Institute of TechnologyVelloreIndia