Catalytic, Kinetic and Thermodynamic Characteristics of an Extracellular Lipase from Penicillium notatum

Abstract

Lipase of Penicillium notatum was purified to electrophoretic homogeneity by ammonium sulphate precipitation, ion-exchange, and hydrophobic interaction chromatography. The purified enzyme displayed a solitary band in the 46-kDa region on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS–PAGE). The pH and temperature optima were found to be 9.5 and 40 °C, respectively. It showed stability over broad pH range (pH 6.0–12) and higher thermal tolerance with half-lives (t _1/2) of 8.25, 3.2, 1.12, and 0.58 h at 40, 50, 60 and 70 °C, respectively. The K _m and V _max values for p-nitro phenyl palmitate (pNPP) hydrolysis were 3.33 mM and 232.6 µmol/mL min⁻¹, respectively. The energy of activation for denaturation E_a(d) was 81.1 kJ/mol, whereas the entropy (ΔS^*), enthalpy (ΔH^*) and free energy (ΔG^*) of thermal inactivation of lipase were recorded to be −0.083 Jmol^−l K^−l, 78.48 and 104.54 kJ/mol, respectively, at 40 °C. The enzymatic activity was substantially improved by Ca²⁺ and Mg²⁺, and suppressed in the presence of Co²⁺ _, Cd²⁺, Pb²⁺ and Fe³⁺ ions to various levels. Exposure to hydrophobic environment did not affect the enzyme stability; however, protease solution deactivated the enzyme. Considering all these properties, this fungal lipase would be an interesting candidate for future organic synthesis application.

Graphical Abstract