Lipase Studies. I. the Hydrolysis of the Esters of Some Dicarboxylic Acids by the Lipase of the Liver. by Adam A. Christman and Howard

The hydrolysis of the esters of the dicarboxylic fatty acids, malonic and succinic, by lipase has not been the subject of careful study. Doyen and Morel (1) observed that serum lipase caused hydrolysis of diethyl succinatc? but the results are difficult of interpretation from a quantitative standpoint. Kastle (2) stated that diethyl succinate was readily hydrolyzed by liver lipase, but cited no quantitative data as to the extent of hydrolysis. He also observed that the metallic salts of the monoethyl cstcrs of the dicarboxylic acids, e.g. sodium ethyl succinate, were not split by the lipase of the liver. He considered that the inactivity of lipase toward this class of compounds was due to the fact that they are ionized and that lipase is unable to attack ionized compounds. Morel and Terroine (3) undertook a comparative study of the hydrolysis of the diethyl esters of malonic, succinic, glutaric, suberic, and sebacic acids by the pancreatic juice of the dog, and concluded that the ease of hydrolysis increased wit,h the increase of molecular weight of the ester up to glutaric acid. The maximum hydrolyses obtained were 2.6 per cent for ethyl malonate and 12.9 per cent for ethyl succinate. It is difficult to interpret their results inasmuch as no very definite details as to the amounts of ester and enzyme used or the dilution employed are given. It would appear, however, that the concentration of ester was such that a considerable part of it must have remained in suspension or emulsion. Moreover, the time (6 to 7 hours in most experiments) was too short to allow the reaction to reach an equilibrium, especially with the high concentration of ester in