The functional and structural stabilization of trypsin by sucrose

Docking and spectroscopic techniques were performed to probe the stabilizing effect of sucrose on the dynamics, structure and activity of trypsin. The thermodynamic folding properties, melting temperature (Tm), enthalpy change (ΔH°) and entropy change (ΔS°) were measured by thermal stability studies to understand the picture of trypsin folding. Sucrose acted as an enhancer for trypsin stability. Fluorescence spectroscopy revealed the static model of the quenching. The number of binding sites was 1. The Absorption, Fluorescence and circular dichroism spectral analysis illustrated that sucrose could protect the native structural conformation of enzyme and prevent the enzyme unfolding. Fluorescence spectroscopy and the molecular docking technique simulation displayed that the hydrogen bonding and Vander Waals forces played a main role in stabilizing the trypsin-sucrose complex, and the number of direct H-bonds between sucrose and trypsin was low; thus, the direct interactions had little contribution in the stabilizing effect and the indirect interactions caused by the preferential hydration were resulting from a molecular mechanism principally causing the stabilizing effects of sucrose.Upon sucrose conjugation, the kcat/Km value of the enzyme was increased. Tm of the trypsin-sucrose complex was increased due to the higher H-bond formation and the lower surface hydrophobicity after sucrose modification. Sucrose acted as enhancers for trypsin stability and activity. The result shows the ability of sucrose to protect the native structural conformation of trypsin. These results explicitly describe that stabilizing sucrose is preferentially excluded from the surface of trypsin, since water has a higher tendency toward favorable interactions with functional groups of trypsin than with sucrose.