STABILITY OF PORCINE AND MICROBIAL LIPASES TO CONDITIONS THAT APPROXIMATE THE SMALL-INTESTINE OF YOUNG BIRDS

In vitro experiments were conducted to study the stability of lipase a ctivities from bacterial, fungal, and animal sources under conditions that approximate the small intestine. Ln the first experiment, the eff ects of preincubation with trypsin (500, 1,000, and 2,000 U/mL), chymo trypsin (200, 400, and 800 U/mL), and trypsin plus chymotrypsin (TC; 2 ,000 U/mL trypsin + 800 U/mL chymotrypsin) for 30 min at 40 C, on lipa se activities from sources of Pseudomonas spp. (PL1, PL2), Chromobacte rium viscosum (CVL), and Aspergillus niger (ANL) were determined. None of the enzymes were inhibited by trypsin. The chymotrypsin decreased the activity of all of the Lipases. The TC had no additional negative effect on the activities of PL1 and PL2; however, ANL and CVL activiti es were further decreased relative to the chymotrypsin only treatment. In the second study, the effects of Na taurodeoxycholate (0.1 to 16 m M) on the activities of PL1, PL2, CVL, ANL, and crude porcine lipase ( CPL) at 23 and 40 C wereevaluated. At 23 C, in order of potency, Na ta urodeoxycholate inhibited the activities of ANL, CPL, and CVL. At this temperature, Na taurodeoxycholate did not inhibit PL1 and PL2. An inc rease in the temperature to 40 C increased the activity of all of the enzymes tested. At 40 C, Na taurodeoxycholate had similar effects on l ipase activities; however, higher Na taurodeoxycholate levels were req uired to inhibit ANL activity, and only a partial inhibition of CPL oc curred. At 23 C, porcine colipase restored the activity of CPL but had no effect on ANL and CVL in the presence of inhibitory levels of Na t aurodeoxycholate. At 40 C, porcine colipase had no effect on Na taurod eoxycholate inhibition of Lipase activity. The results of this study i ndicate that PL is more stable than CVL and ANL, and that colipase add ition has no beneficial effects on microbial lipase activities under c onditions that approximate the avian small intestine.