RESUMEN
The catalytic behavior of a membrane-bound lipolytic enzyme (MBL-Enzyme) from the microalgae Nannochloropsis oceanica CCMP1779 was investigated. The biocatalyst showed maximum activity at 50⯰C and pH 7.0, and was stable at pH 7.0 and temperatures from 40 to 60⯰C. Half-lives at 60⯰C, 70⯰C and 80⯰C were found 866.38, 150.67 and 85.57â¯min respectively. Thermal deactivation energy was 68.87â¯kJâ¯mol-1. The enzyme's enthalpy (ΔΗ*), entropy (ΔS*) and Gibb's free energy (ΔG*) were in the range of 65.86-66.27â¯kJâ¯mol-1, 132.38-140.64â¯Jâ¯mol-1â¯K-1 and 107.80-115.81â¯kJâ¯mol-1, respectively. Among p-nitrophenyl esters of fatty acids tested, MBL-Enzyme exhibited the highest hydrolytic activity against p-nitrophenyl palmitate (pNPP). The Km and Vmax values were found 0.051â¯mM and of 0.054 mmole pNPâ¯mg protein-1â¯min-1, respectively with pNPP as substrate. The presence of Mn2+ increased lipolytic activity by 68.25%, while Fe3+ and Cu2+ ions had the strongest inhibitory effect. MBL-Enzyme was stable in the presence of water miscible (66% of the initial activity in ethanol) and water immiscible (71% of the initial activity in n-octane) solvents. Myristic acid was found to be the most efficient acyl donor in esterification reactions with ethanol. Methanol was the best acyl acceptor among the primary alcohols tested.