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In the present work we studied the catalytic activity of  E. coli  β-Gal confined in a nanoporous silicate matrix (E β-Gal ) at different times after the beginning of the sol-gel polymerization process. Enzyme kinetic experiments with two substrates (ONPG and PNPG) that differed in the rate-limiting steps of the reaction mechanism for their β-Gal-catalyzed hydrolysis, measurements of transverse relaxation times ( T   2  ) of water protons through  1 H-NMR, and scanning electron microscopy analysis of the gel nanostructure, were performed. In conjunction, results provided evidence that water availability is crucial for the modulation observed in the catalytic activity of β-Gal as long as water participate in the rate limiting step of the reaction (only with ONPG). In this case, a biphasic rate vs. substrate concentration was obtained exhibiting one phase with catalytic rate constant ( k   cA  ), similar to that observed in solution, and another phase with a higher and aging-dependent catalytic rate constant ( k   cB  ). More structured water populations (lower  T   2  ) correlates with higher catalytic rate constants ( k   cB  ). The  T   2  - k   cB   negative correlation observed along the aging of gels within the 15-days period assayed reinforces the coupling between water structure and the hydrolysis catalysis inside gels.

Environmental Topology and Water Availability Modulates the Catalytic Activity of β-Galactosidase Entrapped in a Nanosporous Silicate Matrix