Linked Life Data

10194383

Source:http://linkedlifedata.com/resource/pubmed/id/10194383

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
14
pubmed:dateCreated
1999-4-29
pubmed:abstractText
The thermal stability of the cold-active alpha-amylase (AHA) secreted by the Antarctic bacterium Alteromonas haloplanctis has been investigated by intrinsic fluorescence, circular dichroism, and differential scanning calorimetry. It was found that this heat-labile enzyme is the largest known multidomain protein exhibiting a reversible two-state unfolding, as demonstrated by the recovery of DeltaHcal values after consecutive calorimetric transitions, a DeltaHcal/DeltaHeff ratio close to unity, and the independence of unfolding thermodynamic parameters of scan rates. By contrast, the mesophilic alpha-amylases investigated here (from porcine pancreas, human salivary glands, yellow meal beetle, Bacillus amyloliquefaciens, and Bacillus licheniformis) unfold irreversibly according to a non-two-state mechanism. Unlike mesophilic alpha-amylases, the melting point of AHA is independent of calcium and chloride binding while the allosteric and structural functions of these ions are conserved. The thermostability of AHA at optimal conditions is characterized by a Tm of 43.7 degrees C, a DeltaHcal of 238 kcal mol-1, and a DeltaCp of 8.47 kcal mol-1 K-1. These values were used to calculate the Gibbs free energy of unfolding over a wide range of temperatures. This stability curve shows that (a) the specific DeltaGmax of AHA [22 cal (mol of residue)-1] is 4 times lower than that of mesophilic alpha-amylases, (b) group hydration plays a crucial role in the enzyme flexibility at low temperatures, (c) the temperature of cold unfolding closely corresponds to the lower limit of bacterial growth, and (d) the recombinant heat-labile enzyme can be expressed in mesophilic hosts at moderate temperatures. It is also argued that the cold-active alpha-amylase has evolved toward the lowest possible conformational stability of its native state.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0006-2960
pubmed:author
pubmed:issnType
Print
pubmed:day
6
pubmed:volume
38
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
4613-9
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
1999
pubmed:articleTitle
Thermodynamic stability of a cold-active alpha-amylase from the Antarctic bacterium Alteromonas haloplanctis.
pubmed:affiliation
Laboratory of Biochemistry, Institute of Chemistry B6, University of Liège, Belgium. gfeller@ulg.ac.be
pubmed:publicationType
Journal Article, Comparative Study, Research Support, Non-U.S. Gov't