[Catalytic activity of serum lipase during continuous temperature- dependent titrimetry]

The catalytic activity of the pancreatic lipase in serum was measured between 20 degrees C and 37 degrees C by the continuous titrimetric assay. As the temperature was increased, the time course of substrate hydrolysis showed an increasing tendency to become non-linear. The degree of non-linearity and its time of onset depended on the sample, the volume of serum in the assay, and the composition of the triglyceride substrate mixture. Twenty seven series of investigations between 20 degrees C and 32 degrees C (maximal) showed a Q10 value of 1.45 (s = 0.03) and an activation energy of mu = 27.42 +/- 0.565 kJ/mol (6550 +/- 135 cal/mol; mean +/- s). At low assay temperature, the addition of colipase caused a slight deterioration of the reaction kinetics, whereas at higher temperatures it caused a marked improvement in the time course of substrate hydrolysis. We were unable, however, to identify a fixed colipase concentration that would promote a linear reaction irrespective of sample origin and volume. These results show that the assay should be performed at 25 degrees C, and that the test conditions described in 1969 and 1982 are valid without modification. If these conditions are observed, there is no experimental basis for the addition of colipase of the quality commercially available at present.