초록
<P><B>Abstract</B></P> <P>The catalytic behavior of a membrane-bound lipolytic enzyme (MBL-Enzyme) from the microalgae <I>Nannochloropsis oceanica</I> 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 85.57 min respectively. Thermal deactivation energy was 68.87 kJ mol<SUP>−1</SUP>. The enzyme’s enthalpy (Δ<I>Η</I>*), entropy (Δ<I>S</I>*) and Gibb’s free energy (Δ<I>G</I>*) were in the range of 65.86–66.27 kJ mol<SUP>−1</SUP>, 132.38–140.64 J mol<SUP> <SUP>−1</SUP> </SUP> K<SUP>−1</SUP> and 107.80–115.81 kJ mol<SUP>−1</SUP>, respectively. Among <I>p</I>-nitrophenyl esters of fatty acids tested, MBL-Enzyme exhibited the highest hydrolytic activity against <I>p</I>-nitrophenyl palmitate (<I>p</I>NPP). The K<SUB>m</SUB> and V<SUB>max</SUB> values were found 0.051 mM and of 0.054 mmole <I>p</I>NP mg protein<SUP>−1</SUP> min<SUP>−1</SUP>, respectively with <I>p</I>NPP as substrate. The presence of Mn<SUP>2+</SUP> increased lipolytic activity by 68.25%, while Fe<SUP>3+</SUP> and Cu<SUP>2+</SUP> 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 <I>n</I>-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.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Membane-bound lipolytic enzyme (MBL-Enzyme) from microalgae <I>Nannochloropsis oceanica</I>. </LI> <LI> Maximum hydrolytic activity at 50 °C and pH 7.0; stable at pH 7.0 and up to 70 °C. </LI> <LI> Highest hydrolytic activity against <I>p</I>-nitrophenyl palmitate. </LI> <LI> Stable in the presence of water miscible and water immiscible solvents. </LI> <LI> Myristic acid is the most efficient acyl donor in esterification reactions. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>