Expression and biochemical characterization of triose phosphate isomerase (TIM) from psychrophilic bacterium

• Main Author: Lee Sze, Yea
• Format: Monograph
• Language: English
• Published: Universiti Sains Malaysia 2009
• Subjects: R Medicine (General)
• Online Access: http://eprints.usm.my/51168/1/LEE%20SZE%20YEA%20-%2024%20pages.pdf; http://eprints.usm.my/51168/

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.