Mutational and biochemical analysis of Lactobacillus reuteri glucansucrase enzymes

Bacteria are essential for mineralization processes on planet Earth. They live all around us, also on and in our body (skin, mouth, gut), acting amongst others to our food digestion. Lactobacilli are healthy and food grade bacteria. In our mouth they convert sucrose (table sugar) into a sticky biopolymer (α-glucan) using an enzyme (a protein biocatalyst) called glucansucrase. This biological glue allows them to adhere to teeth surfaces. If not brushed away their acid formation from sugar fermentation may cause teeth damage, ultimately resulting in dental plaque formation. I have studied the molecular roles of specific amino acids in the active site of glucansucrase. A large number of glucansucrase mutants that differed in crucial amino acid positions were constructed and characterized. This resulted in strong variations in the structures of the α-glucan products (linkage types, branching degree, and size). The results provide novel insights into structure-function relationships of glucansucrase enzymes and may contribute to future synthesis of tailor-made α-glucans (for food, medicine and research applications) and design of specific inhibitors (for tooth paste, mouth water).