Sugar Rush

New Scientist vol 176 issue 2366 - 26 October 2002, page 34
Once dismissed as mere decoration, sugar molecules turn out to be vital components in life's intricate machinery. Now the race is on to exploit them, says Karen Schmidt

THEY SAY DNA is the 'Blueprint of Life'. It bloody isn't!" growled one British biologist at a recent debate. Perhaps he was speaking figuratively, but it turns out that he is spot on. For all the fanfare surrounding the unveiling of genome after genome, you could be forgiven for thinking that DNA and proteins are all there is to life.
But there is another code out there to be deciphered - a more subtle, more complex alphabet that spells out the structures of massive molecules that subtly monitor and guide the day-to-day lives of the cells in our bodies. And surprising though it may seem, the letters of this alphabet are made of sugar.
You may think of sugars as simple substances you use to sweeten your coffee. But simple sugars can be built into giant molecules called complex sugars that rival DNA and proteins in size and complexity. Until recently, biologists thought that living things used them either mainly for storing energy, as a structural material (in the form of cellulose, for example) or perhaps as mere decorations on the surfaces of cells. But now it has become clear that these molecules are far more than just the icing on the cake.
It turns out that sugars are involved in almost every aspect of biology, from recognising pathogens, to blood clotting, to enabling sperm to penetrate an ovum. The list of things they are already known to do includes regulating the half-life of hormones in the blood, directing embryonic development, and acting as "address codes" for directing traffic of various cells and proteins throughout the body. Biologists are only just beginning to get to grips with these sugars, but as they do they are finding themselves having to rethink long-held ideas about how life works. "This is going to be the future," declares biochemist Gerald Hart of Johns Hopkins University in Baltimore. "We won't understand immunology, neurology, developmental biology or disease until we get a handle on glycobiology."

It's a testament to the importance of sugars that scientists have granted them an "ome" of their own. Just as the "genome" of a creature refers to its entire set of genes and its "proteome" to its set of proteins, the "glycome" of an organism or cell encompasses all the sugars it makes. Still in its infancy, glycomics is slowly revealing its huge cast of sugar-related characters and their myriad roles. "This really is one of the great frontiers in biochemistry," says Hart. "We are where DNA was in 1950."