Promising pancreatic lipase inhibitory activity of a novel tetrapeptide isolated from endophytic Fusarium incarnatum

Pancreatic lipase (PL) is the major enzyme which is required for assimilation of fats during metabolism. It has a dominant role in diet induced obesity. Bioassay guided fractionation of the culture broth of the endophytic fungus, Fusarium incarnatum and subsequent column purification of bioactive aqueous fraction revealed a novel tetrapeptide, 11-amino-2,5,8-triethoxy-4,7,10-trioxo-12-oxa-3,6,9-triazatetradecanoic acid (compound 1) which exhibited a remarkable potential to inhibit PL with IC₅₀ of 2.12 ± 0.11 µg/ml. Further, biochemical characterization of compound 1 exhibited competitive inhibition of PL with an inhibition constant (Ki) of 7.1 µM. The studies involving mode of action of the compound and its effect on the accumulation of lipids in cells was evaluated using 3T3-L adipocyte cell lines. Compound 1 had also reduced the accumulation of lipids in 3T3-L adipocytes by 70% with no adverse cytotoxic effects to 3T3-L adipocyte cells, indicating a prominent aspect in reduction of obesity. Moreover the docking studies of human pancreatic lipase with its substrate (triacyl glyceride), compound 1 and orlistat showed higher affinity of lipase for compound 1. Binding energies for triacyl glyceride, Orlistat and compound 1 was found to be -4.8 kcal/mol, -4.9 kcal/mol and - 5.6 kcal/mol respectively. Thus, this novel tetrapeptide holds promise for clinical evaluation since it exhibits a better inhibition profile than the current anti-obesity drug Orlistat.