Structural and Functional Analysis of Plant Oil-Body Lipase EgLIP1 From Elaeis guineensis.

Abstract

EgLIP1 is an oil-body lipase (EC 3.1.1.3) overexpressed in the fruit mesocarp of Elaeis guineensis (oil palm). Despite its significant role in fruit ripening and the hydrolysis of of triacylglycerol into free fatty acids (FFA) in oil palm, the molecular structure and functional understanding of EgLIP1 are yet to be fully elucidated. Phylogenetic analysis reveals that EgLIP1 shares homology with several plant oil-body lipases. The 3D structure of EgLIP1 was modeled using AlphaFold 2 with high confidence (pLDDT score of 89.7). Structural comparison with Rhizomucor miehei triacylglycerol lipase (RML) reveals that the regions β1, η1, α1, η2, β2, α2, α3, α4, α15, α16, and β15 represent novel insertions unique to EgLIP1, while the overall fold in other regions of the protein remains highly conserved in comparison to RML. Notably, an insertion of residue "PF" was also found in EgLIP1 and its plant orthologs. This insertion is located immediately before the lid domain helix, forming a kink facing toward the active lipase site. Enzyme-membrane surface interaction prediction suggests that α1, α3, α4, α15, and α16 are likely involved in anchoring EgLIP1 at the interface of the phospholipid monolayer of oil bodies. Molecular docking and molecular dynamics (MD) simulation analyses of EgLIP1 with its potential substrate, 1-palmitoylglycerol, demonstrate that the catalytic serine residue S308 and the GX oxyanion hole motif residue T223 can form hydrogen bonds with the carbonyl group of the ligand to initiate a nucleophilic attack on the substrate. Our structure-guided functional studies provide molecular insights into how EgLIP1 associates with oil bodies and catalyzes its potential substrates.