Chaperonin-Inspired Enzyme Protection By Mesoporous Silica

Enzymes can catalyse bioorganic transformations with much higher specificity than traditional chemical catalysts, which makes them valuable for fine chemical and pharmaceutical manufacturing. However, enzymes have evolved to operate within their host cells: most often in neutral, aqueous solutions and at moderate temperatures. Therefore, they tend to have poor stability in chemical reactors that involve high temperatures, acidic or basic conditions, or organic solvents.

In vivo, enzymes are stabilised from high temperature or unfavourable solution conditions by chaperonins. Chaperonins, such as the GroEl/ES complex, help refold partially unfolded proteins within a narrow, cylindrical pore that becomes negatively charged. While chaperonins’ complete mechanisms are complex, we are inspired by some of their fundamental properties when developing materials for enzyme immobilisation.

Mesoporous silica SBA-15 is used as a synthetic chaperonin analogue because of its controlled mesopore diameter and its negatively charged interior surface. Enzymes are immobilised on SBA-15 of different pore diameters, and their stabilities and biocatalytic activities are tested. SBA-15 is shown to be a valuable candidate for enzyme immobilisation, because it can protect enzymes from denaturing conditions. Selected findings include: immobilised myoglobin’s protection from acidic reaction conditions, with activity improvement of up to 350%; immobilised myoglobin’s complete protection from the protease pepsin; immobilised lysozyme’s protection from basic reaction conditions, with activity improvement of up to 200%; and the improvement of immobilised lysozyme’s activity by altering SBA-15’s pore diameter.

More fundamentally, SBA-15 is a useful material for the systematic investigation of enzyme immobilisation parameters because of its highly tuneable pore diameter and its easily functionalised surface. The relative importance of hydropathy, electrostatic attraction, and steric confinement are studied in order to improve the future design of enzyme immobilisation materials.