Ubiquitous in nature, lipases represent an example of enzymes with high versatility. Plant seeds are potential sources of lipase, and they are attracting more attention for specific purposes. In this study, coconut lipase was isolated from germinating coconut seed. Biochemical characterization of coconut lipase was undertaken to reveal its substrate specificity and its subunits properties. By using various chromogenic ester of fatty acids, it was demonstrated that lauric acid is the most preferred substrate for coconut lipase esterase reaction. Calcium ions enhance its activity, whereas other metal ions such as magnesium, nickel, sodium, and potassium reduce it. Electrophoresis under native conditions showed that coconut lipase is a single protein. Since electrophoresis under denaturing conditions revealed four subunits, coconut lipase is likely a complex enzyme. It was further revealed that all subunits are active, as evident in an in-gel hydrolysis assay. However, they also hint that they do not have an equal catalytic rate against the 16-carbon-length palmitate derivative. This finding, thus, opens up a notion that those subunits have different substrates specificity yet to be determined.
Lipases are versatile enzymes with high specificity toward lipid substrate. They have many industrial applications, such as in food, pharmacy, and green fuel. So far, most explored lipases are from microbial and animal sources, whereas those from plants are less studied. The present study aims to characterize ketapang (Terminalia catappa Linn) lipase. The lipase was isolated from germinating ketapang seeds. The activity was determined by hydrolysis of virgin coconut oil (VCO). Biochemical characterization of ketapang lipase includes the optimum temperature, pH, kinetics, metal ions addition, and analysis of substrate specificity. It was shown that ketapang lipase has an optimum temperature of 45 oC, pH 7.5. Ca2+ increases the lipase activity, whereas Na+, K+, Mg2+, Zn2+, Fe2+, and Cu2+ inhibit ketapang lipase to various extents. A comparison of SDS-PAGE and native-PAGE analysis showed that ketapang lipase consists of several protein subunits. A further test by in-gel assay revealed that the 54 kDa, 35 kDa, two bands at ~16 kDa, and 12 kDa proteins showed lipolytic activity against a-naphthyl palmitate substrate. When tested on various chromogenic fatty acid substrates, ketapang lipase showed the highest specificity against short-chain fatty acids (C4 and C8), despite the fact that ketapang oil seed composes mainly of long fatty acid (C18). Since lipases that have high lipolytic activity toward short fatty acids are considered esterases, the esterase activity of ketapang lipase is yet to be determined.
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