Catalytic biofunctional membranes containing site-specifically immobilizedenzyme arrays: a review

Biofunctional membranes normally involve the random immobilization of biomo lecules to porous, polymeric membranes, often through the numerous lysine r esidues on the protein. In this process, bioactivity is significantly decre ased largely due to different orientations of the biomolecule with respect to the membrane or to multiple point attachment. To circumvent this difficu lty, while still taking advantage of the immobilization of biomolecules, si te-specific immobilization of the biomolecule with the active (or binding) site directed away from the membrane is essential. In this review, we summa rize our efforts involving biophysical and bioanalytical chemistry and chem ical engineering, together with molecular biology, to develop and character ize such site-specifically membrane immobilized catalytic enzyme bioreactor s. Site-directed mutagenesis, gene fusion technology, and post-translationa l modification methods are employed to effectuate the site-specific membran e immobilization. Electron paramagnetic resonance, in conjunction with acti ve-site specific spin labels, kinetic analyses, and membrane properties are used to characterize these systems. Biofunctional membranes incorporating site-specifically immobilized biomolecules provide greater efficiency of bi ocatalysis, bioseparations, and bioanalysis. (C) 2001 Elsevier Science B.V. All rights reserved.