Bauke Dijkstra and Lubbert Dijkhuizen of Groningen University have deciphered the structure and the functional mechanism of glucansucrase, the enzyme that is responsible for allowing dental plaque to adhere to teeth.
They say this will stimulate the identification of substances that inhibit the enzyme and which could be added to toothpaste, or even sweets, to prevent tooth decay.
The Groningen researchers analysed glucansucrase from the lactic acid bacterium Lactobacillus reuteri, which is present in the human mouth and digestive tract. The bacteria use glucansucrase to convert sugar from food into long, sticky, sugar chains, which they use to attach themselves to tooth enamel.
The bacterium Streptococcus mutans, which is the main cause of tooth decay, also uses this enzyme. Once attached to tooth enamel, these bacteria ferment sugars, releasing acids that dissolve the calcium in teeth, and promoting the formation of caries.
Using protein crystallography, the researchers have to elucidate the three dimensional (3D) structure of the enzyme. The Groningen researchers were the first to succeed in crystallising glucansucrase. The crystal structure reveals that the folding mechanism of the protein is unique.
Understanding the 3D structure provides detailed insights into the functional mechanism of the enzyme. The enzyme splits sucrose into fructose and glucose, and then adds the glucose molecule to a growing sugar chain. Until now it was assumed that both processes were performed by different parts of the enzyme. However, the model created by the Groningen researchers has revealed that both activities occur in the same active site of the enzyme.
Dijkhuizen thinks specific inhibitors of the glucansucrase enzyme may help to prevent attachment of the bacteria to the tooth enamel.
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Remarkable fold of a 117 kDa glucansucrase fragment: Insights into evolution and product specificity of GH70 enzymes
Vujicić-Žagar, A. et al.