Kinetic studies on pancreatic lipase activity in micellar systems. II. Effect of fatty acid chain length of substrates.

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Abstract
Porcine pancreatic lipase activity toward a series of fatty acid vinyl esters with different chain lengths, solubilized in sodium deoxycholate (NaDC) micelles, was investigated kinetically. The kinetic data could be analyzed on the basis of a fully competitive inhibition mechanism, where substrate-free NaDC micelles act as a competitive inhibitor. The values of inhibition constant (K4), which is the Kd of lipase-NaDC micelle complex, obtained from the reaction of each substrate were in reasonable agreement with one another. The maximum velocity (V) and Km increased with decrease in the fatty acid chain length (C14 .simeq. C12 < C10 < C8). The V Km values indicate that vinyl dodecanoate and tetradecanoate are better substrates than vinyl decanoate and octanoate in this micellar system. The Km/K4 values suggest that the lipase-substrate-solubilizing NaDC micelle complex is less stable than the lipase-substrate-free NaDC micelle complex. The changes in the V and Km values with chain length were ascribed to the difference in the interaction between the substrate molecule and NaDC micelles.

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