The smooth-hound lipolytic system: Biochemical characterization of a purified digestive lipase, lipid profile and in vitro oil digestibility

Abstract In order to identify fish enzymes displaying novel biochemical properties, we choose the common smooth-hound ( Mustelus mustelus ) as a starting biological material to characterize the digestive lipid hydrolyzing enzyme. A smooth-hound digestive lipase (SmDL) was purified from a delipidated pancreatic powder. The SmDL molecular weight was around 50 kDa. Specific activities of 2200 and 500 U/mg were measured at pH 9 and 40 °C using tributyrin and olive oil emulsion as substrates, respectively. Unlike known mammal pancreatic lipases, the SmDL was stable at 50 °C and it retained 90% of its initial activity after 15 min of incubation at 60 °C. Interestingly, bile salts act as an activator of the SmDL. It’s worth to notice that the SmDL was also salt-tolerant since it was active in the presence of high salt concentrations reaching 0.8 M. Fatty acid (FA) analysis of oil from the smooth-hound viscera showed a dominance of unsaturated ones (UFAs). Interestingly, the major n-3 fatty acids were DHA and EPA with contents of 18.07% and 6.14%, respectively. In vitro digestibility model showed that the smooth hound oil was efficiently hydrolyzed by pancreatic lipases, which suggests the higher assimilation of fish oils by consumers.