Synthesis of the rare disaccharide nigerose by structure-based design of a phosphorylase mutant with altered regioselectivity

In the absence of the natural acceptor inorganic phosphate wildtype sucrose phosphorylase from Bifidobacterium adolescentis (BaSP) produces maltose (4-O-alpha-D-glucopyranosyl-D-glucose) and kojibiose (2-O-alpha-D-glucopyranosyl-D-glucose) as sole transfer products. A Q345F exchange switches the enzyme's regioselectivity from 2 to 3 exclusively, yielding the rare sugar nigerose (3-O-alpha-D-glucopyranosyl-D-glucose, sakebiose).