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Adenosine monophosphate (AMP) is an organic compound of adenosine (an adenine base with the sugar ribose) and a single phosphate unit. For a structural representation of adenosine monophosphate, see jafuser's writeup under adenosine triphosphate, which differs (as the name suggests) by having three rather than one phosphate groups. The additional phosphate groups are linked to AMP by high-energy bonds, the breaking of which allows ATP to act as an energy source, yielding Adenosine diphosphate (ADP). It is then possible to break a further bond and obtain AMP:

ADP --> AMP + Phosphate
Or alternatively, directly from ATP
ATP --> AMP + Pyrophosphate
Or as a biproduct of ATP synthesis through combination of two ADP molecules
2 ADP --> ATP + AMP

Concerns over dietary issues such as obesity and diabetes have led food and drink companies to seek out solutions other than salt and sugar to the problem of bitter tastes such as caffeine or those created by the hot cooking processes used for canned goods. Additives such as aspartame attempt to overwhelm the bitter sensation through sweetness, but can leave a bitter aftertaste themeselves. AMP can be used for a different approach and was patented as a "bitter blocker" in April 2003 by biotech company Linguagen- working by blocking the bitter sensation itself rather than mask it with another.

This marks a considerable breakthrough- Professor Linda Bartoshuk of Yale University claims that "The idea of a bitter suppressor is the holy grail. Everybody wants to find it.". However, AMP is not that grail- a universal blocker is unlikely to be possible as humans possess more than 30 bitter-taste receptors specific to uniquely shaped trigger chemicals. Further, research in the past 10 years suggests that the variety of flavours can be determined all over the tongue rather than specific regions and hence determining triggers and targets is complex.

AMP is able to block gustducin, a protein released by taste receptors in the mouth when they detect the compound narigen responsible for the bitter taste of caffeine, ibuprofen and grapefruit. Initial testing of compounds (of which all the effective ones were nucleotides, found naturally in various foods) involved mixing with a dye which turned blue when gustducin was produced- and was found to not do so when AMP was also present. Further testing showed that mice were unable to distinguish plain water from bitter water treated with the compound and researchers even tested it on themselves, finding that coffee tasted "milder, and more mellow".

Crucially, AMP is naturally occuring (as well as its link to energy stores described above, it is found in breast milk and also arises when RNA is broken down by living systems) which should prevent consumer concerns as seen with artificial additives such as Aspartame or Olestra. The ultimate test will of course be the market, with two challenges- replacing salt and sugar in goods without a perceived difference in taste, and finding a market for less bitter versions of beverages such as coffee that people may well prefer as they are.

Thus the most promising use for blockers such as AMP, should they scale to mass production and address a wide range of bitter tastes, wil be in the production of more palatable versions of particularly bitter drugs such as those used for the treatment of HIV, or liquid medicines for children and others unable to swallow pills.

Quotes from: New York Times News Service, BBC News, Daily Mail