Mechanistic Aspects of Pyrophosphorylation Reactions from Model Studies

Abstract

Pyrophosphorylation reactions that mimic pyrophosphorylases have been studied by utilizing nitrophenol as substrate and bistrimethylenediamine cobalt(III) pyrophosphate as the pyrophosphorylating agent. Significant pyrophosphorylation was noted for reactions of 1:1 molar ratio of Co(III)tn2 to PPi (i.e., [Co(III)tn2 PPi] in solution) and nitrophenol. The rate of pyrophosphorylation was significantly reduced for reaction solutions that were 2:1 in molar ratio of Co(III)tn2 to PPi, (i.e., [(Co(III)tn2)2PPi] in solution) and nitrophenol. No appreciable pyrophosphorylation was noted for the pyrophosphate complex, which has a 3:1 molar ratio of Co(III)tn2 to PPi (i.e., [(Co(III)tn2)3PPi] in solution) when reacted with equimolar amounts of nitrophenol. Specific mechanistic features and the possible roles metal ions play in pyrophosphorylase enzymes are highlighted from the results of both ultraviolet–visible (UV-vis) and 31P-nuclear magnetic resonance (NMR) studies.