Pancreatic lipase selectively hydrolyses DPA over EPA and DHA due to location of double bonds in the fatty acid rather than regioselectivity

The enzymatic hydrolysis of canola, anchovy and seal oils with different types and amounts of polyunsaturated fatty acids was measured using porcine pancreatic lipase (PPL) to establish the fatty acid selectivity of PPL. Substrates were subjected to the same conditions of hydrolysis, with percent hydrolysis monitored using Iatroscan and fatty acid selectivity monitored using gas chromatography (GC). Regardless of their distribution on the glycerol backbone, as monitored by 13C nuclear magnetic resonance (NMR), α-linolenic acid (ALA) and docosapentaenoic acid (DPA) were rapidly cleaved by PPL while eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and stearidonic acid (STA) were hydrolysed more slowly. Results show that PPL preferentially hydrolyses ALA and DPA over EPA, DHA and STA, and this selectivity is due to fatty acid rather than regioselectivity. The primary structural factor associated with resistance to PPL appears to be the distance of the first double bond from the ester linkage being hydrolysed.