Corylus avellana non-specific lipid-transfer protein Cor a 8 is a moonlighting enzyme with a new lipase activity

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 it are faster on free fatty acids. Lipase(s) enzymes are required, in oilseed, to hydrolyze the ester bond to free the single molecule of fatty acids. This step, necessary for germination, is the first event to trigger rancidity. Identifying the lipase(s) enzyme 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 family because they were identified as human allergens. Here we show that Cor a 8 - a member of nsLTP - is a novel non-regiospecific lipase that is able to bind to oil-water interfaces and hydrolyze the triacylglycerol (TAGs) ester bonds by a non-canonical active site (non-serine dependent). Molecular modelling and molecular dynamics suggest that Cor a 8 is a moonlighting enzyme not only able to catalyze the hydrolysis of TAGs but also to stabilize the resulting free fatty acids and transport it. 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.