Modifications of emulsions for determination of the rates of lipase-catalysed hydrolysis and intramolecular acyl transfer reactions of lipids

Lamb Pregastric Lipase Activity: Catalyzed Hydrolysis of Dibutyryl-1,2(3)-Propanediols and Butyryl-1(2)-Propanol and Inhibition of the Catalyzed Hydrolysis of Tributyrylglycerol in the Presence of EDTA, LiCl, NaCl and Ethanol

Partially purified lamb pregastric lipase, LPGL, isolated from the tongue and epiglottal region of lamb, was used to catalyze the hydrolysis of tributyrylglycerol, the dibutyryl esters of propanediol and the butyryl esters of propanol at pH 6.5, 35°C. The relative rates of hydrolysis for tributyrylglycerol: dibutyryl-1,2-propanediol: dibutyryl-1,3-propanediol: butyryl-1-propanol: butyryl-2-propanol were 100: 35.4: 12.5: 4.1: 1.1, respectively. Monohydrolysis stoichiometry was observed for tributyrylglycerol and the diesters with saturation kinetics. In contrast, hydrolysis of the monoesters was first-order in substrate. The catalyzed hydrolysis of tributyrylglycerol was ~20% inhibited in the presence of 100 mM EDTA, 10% and 60% in the presence of 1 M NaCl and LiCl, respectively, and ~30% in 10% v/v ethanol.

Early weaning of calves using feedstuffs. A rationalization based on inhibition of lipolysis

The ability of broll (a combination of the wheat-milling byproducts bran and pollard, i.e., a mixture of wheat bran, husk, and flour) and blackstrap molasses (an ingredient of calf feed) to inhibit calf pregastric lipase (CPGL)-catalyzed hydrolysis of tributyrylglycerol (TBG) has been studied in vitro. Lipolysis was measured at pH 6.5 and 37 degrees C (CPGL at 0.02 mg/mL) with stirring at 300 rpm. The broll soaked in Bis-Tris buffer (50 mM, pH 6.5) at 4 degrees C for either 24 h or 15 min, and then added to an emulsion containing TBG, before initiation of the reaction by addition of CPGL, exhibited 22% inhibitory effect. A solution of blackstrap molasses (50%, v/v) exhibited inhibitory effects of 50% in the absence and 45% in the presence of Bis-Tris buffer. The initial rate of lipolysis in the presence of the dialyzed molasses retentate (10%, v/v) increased a little, compared with the same amount of crude molasses, from a mean value of 69% to a mean value of 74%. The results have been discussed in terms of the chemical nature and composition of broll and molasses and their roles as components of feedstuffs used in development of the rumen in early weaning of calves.