The digestion in vitro of triglycerides by pancreatic lipase.

The formation of partial glycerides by the hydrolysis in vitro of triglycerides with pancreatic lipase was first reported by Artom and Reale (1) and then again several years later by Frazer and Sammons (2). In these studies apparently no attention was paid to the isomeric form of the digestion products. Desnuelle et al. (3) further studied the hydrolysis of triglycerides and showed it to be a series of stepwise reactions from triglyceride to diglyceride to monoglyceride to glycerol, fatty acid being released at each step. The quantitative aspects of this work were weakened by their supposition that the hydrolysis was a random one. The pertinent literature in this field has been the subject of an excellent review by Desnuelle (4). The hydrolysis in vivo of triglycerides was reported by this laboratory (5) to be a directed one from triglyceride to 1,2-diglyceride to 2-monoglyceride. Partial conversion of 2-monoglyceride to the 1 isomer also appeared to occur in the intestine. It was likewise reported that at the conclusion of hydrolysis in vitro only the 1 isomer of monoglyceride was present. Subsequently, Borgstriim (6), using methods never previously applied to these types of materials, reported that there is selective formation of 1,2-diglycerides and 2-monoglycerides when triglycerides are hydrolyzed in vitro with pancreatic lipase. In the studies reported here the course of hydrolysis in vitro was found to be the same as hydrolysis in vivo. From some of the characteristics of the reactions, it appears that lipase may be specific for the hydrolytic and esterification reactions occurring at the primary hydroxyl group positions of glycerol.