Hydrolytic (in)stability of phosphate isosteres

For decades enzymatic hydrolysis of nucleotides, a cornerstone of life, was studied extensively along with the chemical hydrolytic reaction. The metabolic instability of nucleotides, in contrast with their enormous chemical stability, triggered development of metabolically stable phosphate isosteres. However, their chemical stability has not been reported. Here, we fill this gap by exploring the hydrolytic stability of the thiophosphate (PS) and dithiophosphate (PS₂) monoester isostere families. Kinetic experiments with uridine-PS and -PS₂ (UMPS and UMPS₂) allow to chart their borders of stability. Furthermore, characterization of several chemical and structural features of UMPS and UMPS₂ provide insights, which explain the dramatically different stability of PS or PS₂ moieties at different positions of the nucleotide phosphate chain. Our conclusions may guide the broad scientific community that applies phosphate isosteres and allow the selection of optimal isosteres.