Biological functions of thiamine derivatives: Focus on non-coenzyme roles

Introduction Thiamine (vitamin B1) is mainly known for its diphosphorylated derivatives, an essential coenzyme in energy metabolism. However, noncoenzyme roles have been suggested for this vitamin for many years. Such roles have remained hypothetical, but recent data from various sources have shed a new light on this hypothesis. First, other phosphorylated thiamine derivatives, most prominently thiamine triphosphate and adenosine thiamine triphosphate, can reach significant levels in Escherichia coli, respectively, during amino acid starvation and energy stress. Although much less is known about these compounds in animals, mammalian cells contain a highly specific soluble thiamine triphosphatase controlling cytosolic thiamine triphosphate concentrations. Second, there is now growing evidence in favour of the existence of thiamine-binding proteins with specific roles in the nervous system, possibly in the regulation of neurotransmitter release. Thiamine and some of its synthetic precursors with higher bioavailability have beneficial effects in several models of Alzheimer’s disease and may be beneficial for patients suffering from Alzheimer’s or Parkinson’s diseases. These effects might be related to non-coenzyme roles of thiamine, possibly involving thiamine-binding proteins. The aim of this review was to discuss biological