Pancreatic lipase when prepared essentially free of co-lipase is strongly inhibited by conjugated bile salts at or above their critical micell concentration. Addition of co-lipase restores activity to the bile-salt-inhibited lipase and gelfilteration experiments indicate that co-lipase in bile salt solution makes a dimer which forms a 1:1 complex with lipase (Morgan, R.G., and N.E. Hoffman, Biochim Biophys Acta, 248, 143-148, 1971). Lipase and co-lipase interact as a stoichiometrical relationship and classified co-lipase interact as a co-enzyme for lipase. The co-lipase is a single chain polypeptide with a molecular weight approximately 11,000 with 5 disulfide bridges and isoelectric point 5.0. (Mayie, M.E., et al, Biochim Biophys Acta, 271, 400-412, 1971).

1. Tributyrin (reagent grade).
2. NaOH, 0.2 M.
3. Lipase (50 Units).
4. Reaction mixture. Dissolve 0.24 g Tris, 2.09 g Sodium tauro-deoxycholate, 0.11 g CaCl2 and 8.76 g NaCl in 800 ml of distilled H2O. Adjust pH to 6.5 with HCl. Bring volume to 1000 ml with distilled H2O.

1. Into the reaction vessel of an automatic titrator pipette 15 ml of the reaction mixture and 0.5 ml of Tributyrin at 25°C.
2. Add 50 potentiometric units of lipase to the reaction vessel.
3. Maintaining the pH at 6.5 (and temperature at 22-24°C), titrate the mixture with 0.2 M NaOH over a 5 min period.
4. Calculate the blank rate.
5. To the reaction vessel add 75 μl of a colipase sample that has been diluted 1:10 with distilled H2O.
6. Titrate the reaction for 5 minutes.
7. Calculate the rate of reaction. (if the net rate is 0.040-0.095 ml/min., continue with the calculation. If the rate is outside this range, adjust the concentration of colipase and reanalyze).