Immobilization of Kluyveromyces lactis ß-Galactosidase on Meso-macroporous Silica: Use of Infrared Spectroscopy to Rationalize the Catalytic Efficiency.

ABSTRACT

Enzyme immobilization on adequate carriers is a challenging strategy. Understanding the enzyme-carrier interactions and their effects on enzyme conformation and bioactivity is critical. In this study, a meso-macropores silica (MMS) was used to immobilize ß-galactosidase from the yeast Kluyveromyces lactis (ß-gal-KL) by physical adsorption. The bioactivity of the immobilized ß-gal-KL was altered, evidenced by the increased Km , decreased Vmax and kcat , and increased activity at alkaline values. By performing infrared spectroscopy analysis and subsequent secondary structure assessment from the amide I band, the immobilized ß-gal-KL suffered a ß-sheet (∼31-35 %) to α-helix (∼15-19 %) transition with increased turns (∼21-22 %) with respect to the free ß-gal-KL having ∼12 % α-helix, ∼42 % ß-sheet, and ∼17 % turns. These findings led us to correlate the observed bioactivity performance to structural alterations to a non-native conformation. The presented line of thought can lead to a better understanding of the reasons causing bioactivity alterations upon enzyme immobilization.