Sensing the sweet smell of saccharides

Japanese researchers develop carbohydrate biosensor.

Although not as well known as nucleic acids or proteins, saccharides and their derivatives, such as glycolipids, are important biochemical species that are involved in a range of complex cellular activities, such as protein folding. Many of the exact functions of these carbohydrates still remain hidden, but this situation may be about to change as a result of work carried out by a team of research chemists from Kyushu University in Japan.

Analysing the cellular expression of saccharides has proved difficult because of their high level of structural diversity. Cellular saccharides have previously been investigated using a family of saccharide-binding proteins known as lectins, but they suffer from a fairly low level of selectivity and therefore can’t form the basis of a high-throughput analysis system. The Japanese researchers wondered whether they could improve the saccharide-detecting ability of lectins by turning them into semi-synthetic biosensors.

To test this idea, the researchers attached an artificial receptor known as phenylboronic acid (PBA), which is capable of binding to 1,2- or 1,3-diol derivatives, onto the lectin Concanavalin A (ConA), near its sugar binding site. They then equipped the PBA with a fluorescent transducer motif. In theory, when a saccharide attaches to the ConA binding site one of its diol units will bind with the PBA, causing the biosensor to fluoresce.

In practice, the researchers discovered that the biosensor would only fluoresce in the presence of certain saccharides, depending on the specific interaction between the ConA binding site, the PBA and the saccharide.

By using a variety of artificial receptors and lectins, the researchers argue that it should be possible to create a range of different biosensors that between them would be able to identify all the saccharides in a cell.

Furthermore, other non-recombinant binding proteins, such as antibodies and receptors, could be used as the basis for novel biosensors, suggests Tony Cass, professor of bioanalytical chemistry at Imperial College London, UK. ’Such reagents would have applications in a variety of areas, such as protein microarrays, intracellular monitoring and implanted sensors,’ he predicts.

Jon Evans