PARTIAL CHARACTERIZATION AND QUANTIFICATION OF PANCREATIC LIPASE IN THE GATROINTESTINAL TRACT OF TOTOABA, Totoaba macdonaldi  

Understanding the utilization of dietary lipids in marine fish is crucial for understanding their energy metabolism. Nevertheless, our knowledge of the biochemical mechanisms that allow marine fish the use of this particular nutrient is rather basic. Pancreatic lipase (PL) is the main digestive lipolytic enzyme in higher vertebrates and is secreted by the exocrine pancreas. A pancreatic lipase has been reported in top minnow (Triportheus sp.), sardine (Sardinella longiceps), cod (Gadus morhua), and turbot (Scophtalmus maximus). Totoaba macdonaldi is a marine sciaenid of the Gulf of California with great potential for aquaculture. Development of aquafeeds for its culture is progressing as quantitative nutritional requirements are established, but lipid levels from 8 to 22% do not seem to affect its growth performance, similarly to red drum, Sciaenops ocellatus, another sciaenid for which lipase is apparently not stimulated by increasing dietary fat content. The present work investigated the molecular mass of pancreatic lipase and quantified its presence along the gastrointestinal tract of T. macdonaldi.

Forty adult totoabas spawned in captivity were donated by the Center for Reproduction of Marine Species of the State of Sonora (CREMES); their mean average weight and total length (± S.D.) were 1477.25 ± 145.37 g and 52.86 ± 1.99 cm, respectively. After obtaining some additional biometric data for the determination of the viscerosomatic index (VSI), hepatosomatic index (HSI), and condition factor (K), the GI tract of fish were dissected and homogenates in a 50 mM Tris-HCl buffer solution (pH 7.5) were obtained. The molecular mass of native lipase and its content in the fish pyloric caeca, as well as in the anterior, middle and posterior GI tract were determined by SDS-PAGE using 10% polyacrylamide gels resolved at a constant voltage of 115V. Lipase activity was determined with a lipase activity assay kit (Sigma-Aldrich, MAK046, St. Louis, MO, USA) using a coupled enzyme reaction resulting in a colorimetric (570 nm) product proportional to the enzymatic activity present. One unit of lipase was the amount of enzyme that generated 1.0 mmole of glycerol from triglycerides per minute. Activity of pancreatic lipase was determined at different pH (6-10) and temperatures (20-60°C).