PEGylation versus glycosylation: effect on the thermodynamics and thermostability of crisantaspase

Thermostability is an important and desired feature of therapeutic proteins and is critical for the success or failure of protein drugs development. It can be increased by PEGylation-binding of poly(ethylene glycol) moieties-or glycosylation-post-translational modification to add glycans. Here, the thermostability and thermodynamic parameters of native, PEGylated, and glycosylated versions of the antileukemic enzyme crisantaspase were investigated. First-order kinetics was found to describe the irreversible deactivation process. Activation energy of the enzyme-catalyzed reaction (E*) was estimated for native, PEGylated, and glycosylated enzyme (10.2, 14.8, and 18.8 kJ mol^-1 respectively). Half-life decreased progressively with increasing temperature, and longer half-life was observed for PEG-crisantaspase (87.74 min) at 50 °C compared to the native form (9.79 min). The activation energy of denaturation of PEG-crisantaspase (307.1 kJ mol^-1) was higher than for crisantaspase (218.1 kJ mol^-1) and Glyco-crisantaspase (120.0 kJ mol^-1), which means that more energy is required to overcome the energy barrier of the unfolding process. According to our results, PEG-crisantaspase is more thermostable than its native form, while Glyco-crisantaspase is more thermosensitive.