Changes in the apparent hydrophobicity of Pseudomonas lipases after heat treatments

The loss in enzyme activity and increase in the apparent hydrophobicity after heating Pseudomonas UICD91 lipases, LI and LII, at 55, 65, or 95°C for 10 min in a phosphate buffer were determined. Both lipases appeared to be heat-sensitive and the loss in enzyme activity followed the order: 95 > 65 > 55°C. However, both lipases exhibited a peak in the percentage increase in apparent hydrophobicity at 65°C, indicating that, at this temperature, a conformational transition in the molecule leads to exposure of hydrophobic groups.