An amino acid produced in the intestine has an important role in regulating sleep in Drosophila (fruit flies), reports a paper published online this week in Nature Communications. The amino acid, called D-serine, is conserved between Drosophila and mammals and the findings could lead to insights into the regulation of sleep.

D-serine was thought to exist only in bacteria until relatively recently, when scientists discovered that this amino acid naturally exists in humans. However, the physiological function of D-serine was unknown, with some studies suggesting a potential role in the human brain.

Yi Rao and colleagues screened Drosophila harbouring different genetic mutations and found a mutant that had significantly disrupted sleep. Studying the genes that were disrupted in this mutant fly line, the authors discovered that genes involved in the synthesis and degradation of D-serine were affected. In the absence of the D-serine synthesizing enzyme, serine racemase (SR), sleep was reduced. The authors also found that, although SR is expressed in both the nervous system and the intestines, only the activity of this enzyme in the intestine was functionally important for sleep regulation.

Further research is needed to determine whether other organs in the body express SR and how exactly an amino acid produced in the gut can influence a process that is traditionally believed to be controlled by the central nervous system.