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Saturday, December 11, 2010

The cause of tooth decay

Researchers from the University of The Netherlands have isolated the enzyme responsible for tooth decay. More specifically, the enzyme ‘glucansucrase’ allows bacteria to glue themselves to tooth enamel, where they secrete calcium-dissolving acids. This may one day lead to a way to prevent dental caries.

Functionally, glucanosucrase splits sucrose (table sugar) into fructose (fruit sugar) and glucose (the sugar used by cells as an energy source), and then uses the products to create a growing chain of glucose. It is these long sticky glucose chains that the bacteria use to attach themselves to teeth.

The team used protein crystallography to generate the 3D structure of glucansucrase. This revealed a couple of surprises. One is that the enzyme is actually composed of two separate protein strands that are assembled into a unique U-shaped fold. The second is that the sucrose separation and the glucose chain assembly are both performed by the same active site within this fold, rather than by separate active sites.

Finally, the researchers discovered that the active site of glucansucrase is virtually identical to that of amylase, the enzyme in our saliva that digests starch. Undoubtedly, glucosesucrase evolved from such a starch-degrading enzyme. Unfortunately, this makes it difficult to construct an inhibitor that would prevent the action of glucansucrase but not that of amylase. The scientists remain hopeful that this can one day be done.