Conformational changes of enzymes adsorbed at liquid-solid interface: relevance to enzymatic activity

FTIR with attenuated total reflectance spectroscopy was used to study in situ adsorption of enzymes at water-solid interfaces to better understand how conformational changes may monitor enzymatic activity. Because the adsorption process depends on hydrophobic and electrostatic interactions, conformational changes were studied as a function of the nature of the adsorbing substrates, which are hydrophobic or hydrophilic in character. The adsorption kinetics of two examples of serine enzymes, alpha-chymotrypsin (alpha-chym) and Humicola lanuginosa lipase (HLL), were studied. The secondary structure and solvation of the adsorbed enzymes were both compared to the dissolved enzymes. The positively charged alpha-chym was adsorbed on a negatively charged hydrophilic support with minor structural changes, but the negatively charged lipase had no affinity for a similar support. Both enzymes were strongly retained on the hydrophobic support. The secondary and tertiary structures of the alpha-chym adsorbed on the hydrophobic support were strongly altered, which correlates to the inhibition of enzymatic hydrolysis. The specific solvation obtained for the adsorbed HLL is consistent with the existence of the open conformer in relation to the enhanced enzymatic activity at the water-hydrophobic interface.