The Thermostable and Multi-functional Enzymes Catalyzing Carbohydrate Molecules Identified from Thermophilic Archaea

Abstract

Thermophilic archaea are known to possess a number of thermostable proteins and enzymes. Therefore, we may find and characterize the potentially useful gene products from genomic data of thermophilic archaea. However, the useful information extracted from the genomic sequence is only estimated data. Thus, the attempts have been made to express the proteins from the genomic data of thermophilic archaea in E. coli. Among over 400 pET-based expression vectors constructed for expression of the genes from thermophilic archaea, Sulfolobus tokodaii strain7 and Pyrococcus horikoshii OT3, approximately 50% of E. coli harboring these vectors indicated to produce thermostable and soluble proteins. Among those successfully expressed, the proteins, activities of which are correlated with the carbohydrate metabolism, have been selected as the first target for analyzing their activities and functions. All enzymes analyzed showed the extreme thermostability, usage of the multiple substrate molecules and utilization of unusual metal cations as cofactor. Also a significant number of the novel enzymatic activities, which have not been previously found in any organism, were detected in S. tokodaii strain7. From these observations, it can be suggested that thermostable enzymes from thermophilic archaea retains ancestral features for the enzymes identified in higher organisms, and these have potential applications in both the industry and basic research.