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Calf Pregastric Lipase Catalyzed Hydrolysis of 4-Nitrophenylalkanoates and Anhydrous Milk Fat: Effect of pH, Temperature and Acyl Carbon Chain Length

Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand

Robyn D. Manuel

Department of Chemistry, The University of Auckland, Private Bag 92019, Auckland, New Zealand

A commercial extract from the tongue and epiglottal region of suckling calf was partially purified to yield a calf pregastric lipase with activity against 4-nitrophenylalkanoate esters (C2-C12) at 37°C, pH 6.5. Maximum activity was detected against the C1O ester, 4-nitrophenyldecanoate. Lipase catalyzed hydrolysis of anhydrous milk fat showed preferential release of butyric acid. Integral values of pH and temperature were selected for determination of full Michaelis-Menten plots for hydrolysis of 4-nitrophenylacetate, and a kinetic surface was derived to characterize the activity of the enzyme preparation over a wide combination of these conditions. This complex surface revealed a region of maximum activity centered on optimal pH (pH 6.0) and temperature (43°C), although optima are not sharply delineated. A pK of 5.7 for the lipase-substrate dissociation constant and an activation energy of 37 kJ mol^–1 were identified.

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