Lee Sze, Yea
(2009)
Expression and biochemical characterization of triose phosphate isomerase (TIM)
from psychrophilic bacterium.
Other.
Universiti Sains Malaysia.
(Submitted)
Abstract
Psychrophiles are organisms that grow rapidly below 20°C. In order to overcome
the inherent challenges in cold, cold-active enzymes with high catalytic efficiency at low
temperature and heat-labile properties were evolved as one of their adaptive strategies. In
this study, triose phosphate isomerase {TIM) of psychrophilic bacterium n9, which was
isolated from sea ice of Antarctic at Casey station, was overexpressed in Escherichia coli
BL21 (DE3) host under IPTG induction and purified to homogeneity for subsequent
biochemical characterization. TIM is a dimeric enzyme that consists of two identical
subunits, each containing about 250 residues. It catalyzes the interconversion of
dihydroxyacetone phosphate and D-glyceraldehyde-3-phosphate in glycolysis. n9 TIM
activities at temperatures range from 20 to 45°C were studied. The optimum temperature
for n9 TIM activity was found to be in the range of 35 to 40°C. While, thermostability
study showed n9 TIM was quite thermostable. It remained stable at 40°C after 2 hours
incubation and was gradually inactivated at 50°C. These suggest n9 TIM might not
possess psychrophilic features. Other than that, comparative protein sequence analysis
that was performed on TIM sequences from psychrophilic, mesophilic, thermophilic and
hyperthermophilic bacteria revealed an amino acid property groups preference in
psychrophilic and mesophilic TIM as compared to thermophilic and hyperthermophilic
TIM. The deeper understanding of strategies evolved by TIM enzymes that adapted to
varied environments provides contributive information for further studies on those
valuable cold-adapted enzymes.
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