Construction of a fully active truncated alternansucrase partially deleted of its carboxy-terminal domain

Recombinant expression of the large alternansucrase (2057 amino acids) was hindered in E. coli due to poor enzyme solubility and protein degradation. The effects of deletions of the alternansucrase C-terminal CW-like and APY repeated motifs on enzyme solubility and specificity were investigated. A truncated variant deleted of the APY repeats but harboring four C-terminal CW-like repeats displayed a high specific activity and the same specificity of product synthesis as the native enzyme. It is more soluble and suffers less degradation than full length alternansucrase. Hence this truncated variant is a promising tool for the further structural and kinetic study of this interesting enzyme.