Clue to fighting tooth decay found

Behind the Headlines

Wednesday December 8 2010

The enzyme is produced by the bacteria that form plaque

The Daily Telegraph suggests that the dentist’s drill “could be consigned to history” after researchers worked out the structure of an enzyme that allows bacteria to cling to the teeth.

This complex laboratory research has identified the three-dimensional structure of the glucansucrase enzyme, which is produced by the bacteria that form plaque. The researchers identified the sites on the enzyme that allow it to bind to sugars. This creates molecules that allow the bacteria to stick to teeth.

This knowledge may eventually help researchers to find molecules that can stop this enzyme from working, and therefore reduce the risk of plaque and cavities forming. However, such developments will require a lot more research, and this will take time.

 

Where did the story come from?

The study was carried out by researchers from the University of Groningen in The Netherlands. Funding was provided by Senter Innovatiegerichte Onderzoeksprogramma’s. It was published in the peer-reviewed journal Proceedings of the National Academy of Sciences of the USA.

The Daily Telegraph generally covered the study well, but it is premature to suggest that “the terror of the dentist’s drill could be consigned to history”.

 

What kind of research was this?

This was laboratory research looking at an enzyme called glucansucrase, which is involved in the process of tooth decay.

Bacteria in our mouths ferment sugar from the food we eat, creating acids that can dissolve tooth enamel. The bacteria produce glucansucrase enzymes. These help the bacteria to make long chains of sugar molecules (called polysaccharides), which allow the bacteria to stick to the teeth. These polysaccharides also allow plaque to form on the teeth. Plaque is a layer of bacteria and other material produced by the bacteria on the tooth surface.

Molecules that could stop the bacterial glucansucrase enzymes from working could potentially reduce tooth decay by reducing the ability of bacteria to stick to the teeth, preventing the build-up of plaque. However, no suitable molecules have been identified that can do this without affecting the body’s own carbohydrate-digesting enzyme, amylase, which breaks down the starch found in foods like potatoes or bread. In this study the researchers wanted to examine the three-dimensional shape of the glucansucrase enzyme, as they believed this could help them to identify molecules that would bind to the enzyme and stop it working.

 

What did the research involve?

The researchers extracted active glucansucrase enzyme from the plaque-forming bacteria Lactobacillus reuteri 180. For their experiments they isolated the part of the enzyme that binds to sugars and joins them together in a long chain of sugars (polysaccharides) which help the bacteria to stick to the teeth.

The researchers used a technique called X-ray crystallography to look at the structure of this active part of the glucansucrase enzyme. This involved making crystals of the protein, and shooting X-rays at the crystals. The crystals deflect the X-rays, and the pattern of deflection allows researchers to determine the three-dimensional structure of the protein.

The researchers looked at the structure of the active part of the glucansucrase enzyme by itself, and also when it was bound to sugars such as sucrose and maltose. Finally, when they identified which part of the enzyme binds to the sugars, they changed individual amino acids (the building blocks of protein) in this region, to see which amino acids were essential for binding to the sugars.

 

What were the basic results?

The researchers were able to identify the three-dimensional structure of the active part of the glucansucrase enzyme. The enzyme’s structure showed certain similarities with other sugar-binding enzymes, but also some differences. The researchers were also able to identify the “active site” of the enzyme, which allows it to bind to sugars and add them to a growing chain of sugars to form polysaccharide molecules. They also identified specific amino acids within this active site that are essential for the enzyme to work.

 

How did the researchers interpret the results?

The researchers conclude that their study has shown the “molecular details” of the glucansucrase enzyme, and how it interacts with sugars. Based on their findings they also suggest areas of the enzyme that could be targeted by molecules to potentially inhibit the formation of plaque and prevent cavities.

 

Conclusion

This research has furthered scientists’ understanding of the three-dimensional structure of an enzyme involved in plaque formation on the teeth. This may eventually help researchers to develop molecules that can stop this enzyme from working, and therefore reduce the risk of plaque and cavity formation.

By investigating inhibitory substances that are designed specifically to block glucansucrases it is possible that drugs could be developed that don’t have the side effect of inhibiting our body’s own carbohydrate-digesting enzymes in the mouth, which are needed to digest starch. However, such developments will require a lot more research, and this will take time.

It is premature to suggest that “the terror of the dentist’s drill could be consigned to history”.

Analysis by Bazian

Edited by NHS Choices

Links to the headlines

Discovery may help tooth decay. The Daily Telegraph, December 6 2010

Links to the science

Vujičić-Žagara A, Pijninga T, Kraljb S, et al. Crystal structure of a 117 kDa glucansucrase fragment provides insight into evolution and product specificity of GH70 enzymes. PNAS 2010, early edition

Further reading

 Walsh T, Worthington HV, Glenny AM, Appelbe P, Marinho VCC, Shi X. Fluoride toothpastes of different concentrations for preventing dental caries in children and adolescents. Cochrane Database of Systematic Reviews 2010, Issue 1

Pereira-Cenci T, Cenci MS, Fedorowicz Z, Marchesan MA. Antibacterial agents in composite restorations for the prevention of dental caries. Cochrane Database of Systematic Reviews 2009, Issue 3 

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