The Contrast Of Catalytic Efficiency Of Trehalose-6-phosphate Synthase From Arthrobacter Sp.Cjts And Escherichia Coli At Low Temperature

Trehalose is a nonreducing disaccharide which could protect organisms from being damaged in various stress conditions such as desiccation, dehydration, heat, cold, oxidation and osmotic stress. This sugar is present in variety of organisms except higher animals. The main pathway of trehalose's biosynthesis is the otsA/otsB pathway. The gene otsA encodes trehalose-6-phosphate synthase, which produce trehalose-6-phosphate and UDP with the substrates of glucose-6-phosphate and UDP-glucose. The function of OtsB is to produce trehalose using trehalose-6-phosphate. As the important roles of the substrate and product of OtsA inorganisms' survival and growth——UDP-glucose serves as a crucial molecule in thetransmission of cold signal, and trehalose-6-phosphate regulates the carbohydrate'smetabolism in vivo——it is necessary to do a research on the catalytic efficiency ofOtsA of different organisms from different environmental conditions.The Arthrobacter sp.Cjts from cold environment and Escherichia coli from common environment were chosen to do this research. Analyzing a series of enzymological parameters in different temperatures could results in OtsA from Arthrobacter sp.Cjts is superior to that from Escherichia coli, which could set a foundation to the mechanism research of cold-resistant.The otsA genes from Escherichia coli and Arthrobacter sp.Cjts were amplified respectively by PCR and transformed into host bacteria to express the recombined proteins, which were then isolated and purified by affinity chromatography and their catalytic activity were measured.Analyzing the different catalytic efficiencies of OtsA from different organisms at low temperature led to the result that OtsA from Arthrobacter sp.Cjts is more adaptable to low temperature than that from Escherichia coli. The adaptation dependson OtsA's affinity to UDP-glucose(Km) rather than catalytic constant(Kcat)——whenthe temperature fell from 30℃to 16℃, Km of Escherichia coli's OtsA rose from 4.3599 to 9.5891 while that of Arthrobacter sp.Cjts's OtsA fell from 10.6766 to 2.2331, and Kcat fluctuated rulelessly——which infers that Arthrobacter sp.Cjts'smore adaptability to low temperature than Escherichia coli partly derives from OtsA's higher affinity to UDP-glucose in low temperature.