Complicated effects of a zwitterionic polymer containing dimethyl chains on the structures, activities and stabilities of different enzymes

Abstract

• Interactions of three enzymes with zwitterionic polymer pID are extensively studied. • pID has different effects on activities & stabilities of lipase, lysozyme & catalase. • pID quenches intrinsic fluorescence of the enzymes by static quenching mechanism. • pID causes different changes in conformations and microenvironments of enzymes. Zwitterionic polymers have been reported to stabilize proteins because of their highly hydrophilic feature. However, we herein report the complicated effects of a zwitterionic polymer containing dimethyl chains (pID) on the activity, stability and structure of three different enzymes, i.e., Candida rugosa lipase (CRL), lysozyme (LYS) and catalase (CAT) via activity assays and spectroscopic analysis. Activity assays reveal that pID reduces LYS activity at concentrations >1.0 wt%, but it increases the activities of the other two enzymes, CRL and CAT. Particularly, 1.55 times of activity increase is observed for CRL at 5.0 wt% pID. Moreover, pID significantly enhances the thermal stability of CRL, but it is not conducive to the stabilization of LYS and CAT. Spectroscopic analysis unveils that the binding of pID quenches the intrinsic fluorescence of the enzymes via a static quenching mechanism. Thermodynamic analysis identifies both hydrophobic and electrostatic interactions in the binding of pID to the enzymes. Synchronous fluorescence studies reveal that pID causes different conformational changes in the enzyme microenvironments. Taken together, the complicated effects of pID on the enzymes are brought from the different molecular interactions with the enzymes.