The Gastric Lipase in Man

Abstract

Summary.A reexamination has been carried out of the problems concerned with the gastric lipase in man, mainly with pure triglycerides as substrates. Both in vitro and in vivo experiments were undertaken. The optimum pH for gastric lipase towards tripropionin, tributyrin and tricaproin in systems without the addition of CaCl2 is found to be between 5.5 and 5.8. With an increasing number of C‐atoms in the fatty acids there is an evident displacement of the optimum pH to the alkaline side, the optimum pH for tricaprin, trilaurin and tristearin being 7.2, 7.3 and 7.9 respectively. Addition of CaCl2 to the enzyme‐substrate systems causes definite activation of the hydrolysis of trilaurin and tristearin at pH lower than 7, and the optimum pH is shifted 1.5 to 2 pH units to the acid side. The relative activities of gastric lipase towards different triglycerides have been computed. Tributyrin is split with the greatest initial velocity, whereas the relative activities towards the solid triglycerides are very small. Experiments on the stability of gastric lipase at 40° C at different pH values show that gastric lipase is a very stable enzyme in the acid medium. The lipolysis stated in our experiments in vivo is according to our opinion due to a specific gastric lipase and not to a regurgitated pancreatic lipase. Experiments in vivo with test meals containing pure triglycerides show that only the lower triglycerides are split to an appreciable extent during the experimental period of 25 min. Under similar experimental conditions there seems to be hardly any difference between the degrees of hydrolysis of fatty substances in the stomach by means of the gastric lipase in adults and in children. Under similar experimental conditions in children there is a tendency to a higher splitting in the stomach of cow‐butter fat than of woman's milk fat when these fats are given in test meals.