Effect of Biosilicification using R5 Peptide Tag on Enzyme Stabilization and Activity

Abstract

Effective immobilized techniques provide a great improvement on the stabilization of enzyme activity. In this study, biosilicification catalyzed by the silaffin R5 peptide from marine diatom Cylindrotheca fusiformis was investigated for the feasible evaluation of enzyme immobilization and stabilization. Glutathione S-transferase (GST) as the model enzyme was used, and GST and R5 tagged GST gene (GST-R5, R5-GST-R5) were amplified by PCR and inserted into the pET-28 a(+) vector for the expression in Escherichia coli BL21(DE3). Biosilicification was performed by adding tetramethoxysilane (TMOS) to R5 tagged proteins, which resulted in silica particle precipitation at ambient temperature and pressure in vitro. The silica nano-beads (about 200 nm in diameter) retained high GST activity. Loading efficiency (percent of enzyme with precipitated silica) and immobilization yield of R5 tagged GSTs (GST-R5, R5-GST-R5) increased as pH decreased. Maximum immobilization yield with R5-GST-R5 (95.48%) at pH 6.0 were observed.