Nanoparticle Size Influences Localized Enzymatic Enhancement—A Case Study with Phosphotriesterase

Enhancements in enzymatic catalytic activity are frequently observed when an enzyme is displayed on a nanoparticle (NP) surface. The exact mechanisms of how this unique interfacial environment gives rise to this phenomenon are still not understood, although evidence suggests that it can help alleviate some of the enzyme’s rate-limiting mechanistic steps. The physicochemical limitations that govern when this process arises are also not known including, in particular, the range of NP size and curvature that are associated with it. To investigate the latter, we undertook a case study using the enzyme phosphotriesterase (PTE) and a series of differentially sized gold NPs (AuNPs). PTE, expressed with a terminal hexahistidine sequence, was ratiometrically coordinated to a series of increasing size AuNPs (diameter ≃ 1.5, 5, 10, 20, 55, 100 nm) surface-functionalized with Ni2+-nitrilotriacetic acid ligands and its activity assayed in a comparative format versus that of equivalent amounts of free enzyme controls. ...