Tooth decay to be a thing of the past?

Washington: Tooth decay could soon be a
thing of the past, say scientists who claim to have deciphered
the structure and functional mechanism of glucansucrase enzyme
which is responsible for dental plaque sticking to teeth.

A team at University of Groningen, led by Prof Bauke
Dijkstra and Prof Lubbert Dijkhuizen, has claimed the findings
would stimulate identification of substances that inhibit the
enzyme, the `PNAS` journal reported.

Just add that substance to toothpaste, or even sweets,
and caries will be a thing of the past, say the scientists.

In their study, the scientists analysed glucansucrase
from the lactic acid bacterium Lactobacillus reuteri, which is
present in the human mouth and digestive tract. The bacteria
use the glucansucrase enzyme to convert sugar from food into
long, sticky sugar chains. They use this glue to attach
themselves to tooth enamel.

The main cause of tooth decay, bacterium Streptococcus
mutans, also uses this enzyme. Once attached to tooth enamel,
these bacteria ferment sugars releasing acids that dissolve
the calcium in teeth. This is how caries develops.

Using protein crystallography, the researchers were
able to elucidate the three dimensional (3D) structure of the
enzyme. They are the first to succeed in crystallizing
glucansucrase. The crystal structure has revealed that the folding
mechanism of the protein is unique. The various domains of the
enzyme are not formed from a single, linear amino acid chain
but from two parts that assemble via a U-shaped structure of
the chain; this is the first report on such a folding
mechanism in the literature.

The unravelling of the 3D structure provided the
researchers with detailed insight 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.

"The various inhibitors studied not only blocked the
glucansucrase, but also the digestive enzyme amylase in our
saliva, which is needed to degrade starch," Prof Dijkhuizen


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