On the evolutionary origins of the bacterial phosphoenolpyruvate:sugar phosphotransferase system

The genes encoding the proteins of the fructose-specific phosphotransferase system (PTS) of Rhodobacter capsulatus were sequenced, and the deduced amino acyl sequences of the energy-coupling protein, Enzyme I, and the transport protein, Enzyme IIfru, were compared with published sequences. Enzyme I was found to be homologous to pyruvate:phosphate dikinase of plants, while Enzyme IIfru was found to be homologous to the insulin-responsive glucose facilitator of mammals. The evolutionary and functional implications of these findings are discussed.