High hydrostatic pressure (HHP) stabilized glucose oxidase (GOx) from Aspergillus niger and xanthine oxidase (XOx) from bovine milk against thermal inactivation. Stability increased 50 times for native GOx at 240 MPa and 74.5 C and 9.5 times for native XOx at 300 MPa and 70.0 C compared to the controlled atmospheric pressure at the same temperature. The stabilizing effect of HHP was highest at 74.5 or 70.0 C where the activation volume (V) of inactivation was 57.0 12.0 cm3 mol-1 or 28.9 2.9 cm3 mol-1 for GOx or XOx respectively. Positive V for all the treatment confirmed that HHP favored GOx and XOx stabilization.A second approach to increase GOx and XOx stability involved crosslinking aniline or benzoate. At atmospheric pressure, the thermal stability of GOx was 1.1 times higher after aniline modification (13.4 0.8 min-1), while it was 0.9 times lower upon modification with benzoate (16.2 1.0 min-1) compared to the native GOx (15.3 0.4 min-1) at 80.0 C. At HHP, the thermal stability of the aniline- and benzoate-modified GOx was higher than the native GOx and it increased 3.7-fold after aniline modification and 2.8-fold after benzoate modification compared to the native GOx at 240 MPa at 80.0 C. However, the thermal stability of XOx remained unaffected after 8 1 modifications of carboxyl side groups per XOx monomer with aniline, or 12 5 modifications of amino side groups per XOx monomer with benzoate using DSC analysis.At HHP and in the presence of substrates, the catalytic activity of the aniline-modified GOx resulted in the fastest reaction followed by the benzoate-modified and native GOx at all the studied temperatures. At 180 MPa and 69.1 C, the aniline-modified GOx catalyzed the oxidation of glucose 11-fold faster compared to the reaction of the same enzyme at atmospheric pressure and 25 C. Negative V were assessed for all the studied temperatures which confirmed HPP favored activation of the enzymes. The highest activation energy was 34.7 2.7, 42.3 3.7, or 39.4 2.4 kJ mol-1 at 180 MPa for native, aniline-, or benzoate-modified GOx respectively.