The action of pancreatic lipase on stereoisomeric triglycerides

d-, l-, and dl-α,β-dipalmitin were acylated with oleic acid to the corresponding oleoyl- d-, l-, and - dl-α,β-dipalmitin. Each of these isomers yielded, after hydrolysis with pancreatic lipase, an equimolecular mixture of oleic and palmitic acids, and an optically inactive mixture of diglycerides containing oleic and palmitic acids in the molar ratio of 1:3. After hydrolysis of triolein with pancreatic lipase, the α,β-diolein formed was found to be optically inactive. These results confirm the conclusion of other workers that pancreatic lipase is specific for the hydrolysis of the primary ester linkages in triglycerides. The present evidence further establishes that the enzyme shows no preference for one of the primary ester groups over the other, but hydrolyzes both at the same rate. The mechanism of enzymic hydrolysis of the primary ester groups is therefore random and not stereospecific.