Mode of Action of Pancreatic Lipase*

In the past the specificity of lipase action for fats has been to some extent taken for granted. Pancreas extracts were known to hydrolyze all the ordinary glycerides (except possibly the stearins) and this behavior defined the enzyme lipase. There have been good reasons for supposing that stearins constituted no exception in principle, but were merely attacked very slowly. Actually, tristearin was split so poorly by otherwise powerful preparations of pancreas lipase that its digestion, when observed at all, was entirely out of line with what might have been expected for a commonly occurring edible fat. We have recently shown, however, that the hydrolysis of mono-, di-, or tristearin can be carried out at a rate quite comparable to that found with the other fats, provided special conditions are maintained involving a high temperature and a good emulsion (1). The temperature of digestion is best kept at 40” or over. The emulsion is made by dissolving the stearin in a hot mixture of bile and glycerol, cooling down the solution until it is pasty, and then diluting with the required buffer.’ This technique, as proved by the rapid digestion of tristearin, ought to give a more complete picture of the range of lipase activity on other substrates than has hitherto been obtainable.