Modification of the Transfructosylation Activity of Bacillus Subtilis Levansucrase by Solvent Effect and Site-Directed Mutagenesis

A significant modification of the transfructosylation specificities of Bacillus subtilis levansucrase was obtained by two methods. Firstly, in concentrated solution of organic solvents this enzyme displays only its polymerase activity. Secondly, amino acid substitutions of the catalytically essential residue Arg331 generate levansucrase variants which have lost the ability of the wild-type enzyme to synthesize levan from sucrose, but have preserved the sucrose hydrolytic activity and the ability to synthesize the trisaccharide kestose. The latter reaction was investigated using a Lys331-variant. The aim of the present study is to contribute to a better understanding of fructan synthesis in bacteria and to provide a way to investigate the hypothesis that the enzymes involved in fructan synthesis by bacteria and plants have a common ancestor.