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@ARTICLE{Duy:49011,
author = {Duy, C. and Fitter, J.},
title = {{T}hermostability of {I}rreversible {U}nfolding
alpha-{A}mylases {A}nalyzed by {U}nfolded {K}inetics},
journal = {The journal of biological chemistry},
volume = {280},
issn = {0021-9258},
address = {Bethesda, Md.},
publisher = {Soc.},
reportid = {PreJuSER-49011},
pages = {37360 - 37365},
year = {2005},
note = {Record converted from VDB: 12.11.2012},
abstract = {For most multidomain proteins the thermal unfolding
transitions are accompanied by an irreversible step, often
related to aggregation at elevated temperatures. As a
consequence the analysis of thermostabilities in terms of
equilibrium thermodynamics is not applicable, at least not
if the irreversible process is fast with respect the
structural unfolding transition. In a comparative study we
investigated aggregation effects and unfolding kinetics for
five homologous alpha-amylases, all from mesophilic sources
but with rather different thermostabilities. The results
indicate that for all enzymes the irreversible process is
fast and the precedent unfolding transition is the
rate-limiting step. In this case the kinetic barrier toward
unfolding, as measured by unfolding rates as function of
temperature, is the key feature in thermostability. The
investigated enzymes exhibit activation energies (E(a))
between 208 and 364 kJmol(-1) and pronounced differences in
the corresponding unfolding rates. The most thermostable
alpha-amylase from Bacillus licheniformis (apparent
transition temperature, T(1/2) approximately 100 degrees C)
shows an unfolding rate which is four orders of magnitude
smaller as compared with the alpha-amylase from pig pancreas
(T(1/2) approximately 65 degrees C). Even with respect to
two other alpha-amylases from Bacillus species (T(1/2)
approximately 86 degrees C) the difference in unfolding
rates is still two orders of magnitude.},
keywords = {Animals / Aspergillus oryzae: enzymology / Bacillus:
enzymology / Circular Dichroism / Enzyme Stability / Hot
Temperature / Kinetics / Protein Denaturation / Protein
Folding / Swine / Thermodynamics / Transition Temperature /
alpha-Amylases: chemistry / alpha-Amylases: metabolism /
alpha-Amylases (NLM Chemicals) / J (WoSType)},
cin = {IBI-2},
ddc = {570},
cid = {I:(DE-Juel1)VDB58},
pnm = {Neurowissenschaften},
pid = {G:(DE-Juel1)FUEK255},
shelfmark = {Biochemistry $\&$ Molecular Biology},
typ = {PUB:(DE-HGF)16},
pubmed = {pmid:16150692},
UT = {WOS:000233044500009},
doi = {10.1074/jbc.M507530200},
url = {https://juser.fz-juelich.de/record/49011},
}