Functional properties of immobilized pyridoxal 5′-phosphate-dependent enzymes probed by absorption microspectrophotometry

Functional properties of the pyridoxal 5'-phosphate-dependent enzymes tryptophan synthase and O-acetylserine sulfhydrylase immobilized by crystallization or encapsulation in wet porous silica gels were investigated by absorption microspectrophotometry. The enzyme behavior exhibits a few striking differences in the crystals and silica gels compared to solution, likely due the constraints of either lattice forces or silica matrix on the conformational equilibria that accompany catalytic events. The results define the experimental conditions to accumulate metastable catalytic species in the crystalline state, to develop bioreactors with immobilized enzymes and to slow down protein folding processes.