Phosphatase-Mediated Hydrolysis of Linear Polyphosphates

Polyphosphates are a group of phosphorus (P) containing molecules that are produced by a wide range of microorganisms and human activities. Although polyphosphates are ubiquitous in aquatic environments and are of environmental significance, little is known about their transformation and cycling. This study characterized the polyphopshate-hydrolysis mechanisms of several representative phosphatase enzymes and evaluated the effects of polyphosphate chain length, light condition, and calcium (Ca²⁺). ³¹P nuclear magnetic resonance (NMR) spectroscopy was used to monitor the dynamic changes of P molecular configuration during polyphosphate hydrolysis and suggested a terminal-only degradation pathway by the enzymes. Such mechanism enabled the quantification of the hydrolysis rates by measuring orthophosphate production over time. At the same initial concentration of polyphosphate molecules, the hydrolysis rates were independent of chain length. The hydrolysis of polyphosphate was also unaffected by light condition, but was reduced by the presence of Ca²⁺. The released orthophosphates formed Ca-phosphate precipitates in the presence of Ca²⁺, likely in amorphous phases. Results from this study lay the foundation for better understanding the chemical processes governing polyphosphate transport and transformation in various environmental settings.