Traditional approaches to stabilizing enzymes outside cells often rely on harsh chemical reactions to covalently link the enzymes to various matrices, or alternatively employ enzyme adsorption/encapsulation in non-open porous supports. These approaches often substantially lower the activity per enzyme molecule; i.e. the specific activity. Functionalized, open nanosupports offer promise for mimicking the crowded, enzyme-friendly cellular environment to enhance enzyme specific activity and stability.
Work at Pacific Northwest National Laboratory, US, has demonstrated that multiple enzymes exhibit much enhanced specific activities and stabilities when spontaneously entrapped in functionalized mesoporous silica (Nanotechnology 17 5531). The appropriate functionalized groups within the uniform and open nanopores (pore size ~ 30 nm) facilitate enzyme immobilization without requiring any harsh conditions.
Once inside the pores, enzyme molecules do not escape, yet the enzyme substrates and products can freely enter and leave the pores. High local concentrations of enzymes in the nanomaterials provide a crowded environment for each enzyme molecule that may be responsible for enhancing stability and activity.
Recombinant DNA methodologies will facilitate the production and optimization of enzymes in more advanced functionalized nanoporous materials. Cell-free protein production approaches capable of making hundreds of protein variants each day should yield insights that lead to further improved enzyme specific activities and stabilities.
It may eventually be possible to optimize enzyme-based molecular machines in new nanomaterials to catalyze complex biological reactions to produce bioenergy or remediate toxic pollutants.