The histidyls catalyse also the formation of other phosphate containing products. The products from these reactions include orthophosphate (from hydrolysis) and pyrophosphate (from phosphate anhydride bond formation) (Figure ). The formation of orthophosphate and pyrophosphate were catalysed by histidyl peptides (SI Figure and). In the above experiments, we used a 25-fold excess of the glycerol in order to direct phosphorylation predominantly onto the organic nucleophile. At a lower excess of glycerol of 10-fold (1.30 mmol, SI Section S3. 19) we still observed catalysis of phosphate transfer to glycerol (SI Figure ). But in addition, we observed a broader range of phosphorylation reactions which compete with the phosphorylation of the glycerol. The products from these reactions include orthophosphate, pyrophosphate and triphosphate (SI Figure ).