Unravelling a new enzymatic activity of non-specific lipid transfer protein Cor a 8: A novel lipase from hazelnuts

The high-fat content of hazelnuts, mainly triglycerides, makes them prone to lipid oxidation during storage, which has a big impact on their sensory and nutritional quality. The chemical pathways leading to hazelnut oxidative rancidity have been well characterized and are faster on free fatty acids. Lipase(s) enzymes are required in oilseeds to hydrolyse the ester bonds to free the single molecule of fatty acids. This step, necessary for germination, is the first event that triggers rancidity. Identifying the lipase(s) in hazelnuts and the biochemical pathways involved in rancidity would lead to an effective strategy to prevent fat deterioration. Different proteins have been characterized in hazelnut seed and great interest has been risen towards the non-specific lipid transfer protein (nsLTP) family because they were identified as human allergens. Here we show that Cor a 8 – a member of nsLTPs – is a novel non-regiospecific lipase able to bind to oil-water interfaces and hydrolyse the triacylglycerol (TAG) ester bonds by a non-canonical active site (non-serine dependent). Molecular modelling and molecular dynamics suggest that Cor a 8 is not only able to catalyse the hydrolysis of TAGs but also to stabilize the resulting free fatty acids within the active site. Cor a 8 homologues are present in all land plants, but the specific catalytic amino acids are found only in angiosperms, suggesting an evolutionary adaptation for lipid metabolism unique to flowering plants. This study sets the foundation for understanding this new lipid metabolism in plants and its role in rancidity development.