Encapsulation of catalase into nanochannels of an inorganic composite membrane

Enzymes, especially those known as membrane proteins existing in plasma membranes, direct important and complicated reactions in living bodies. Thus, attempts have been made to extract such enzymes from living bodies, and immobilize and accumulate them on supports to effectively use their functions for catalysis [M. Hartmann, Chem. Mater. 17 (2005) 4577-4593]. However, enzymes extracted from living bodies tend to aggregate in the absence of detergents or at high concentrations, resulting in a loss of their activities [Y. Urabe, T. Shiomi, T. Itoh, A. Kawai, T. Tsunoda, F. Mizukami, K. Sakaguchi, ChemBioChem 8 (2007) 668-674]. We have, however, succeeded in assembling a highly durable membrane capable of high-density accumulation and providing a regular array of catalase by encapsulating it in mesoporous silica synthesized in the pores of an alumina membrane. The artificial biomembrane showed not only activity similar to that of the native catalase for the decomposition of H₂O₂ but also much higher stability; the catalase immobilized in the membrane still retained its original activity even after being employed 160 times in decomposing H₂O₂, whereas the native lost its activity after 40 cycles.