Human gastric lipase. Effects of fatty acid and bovine serum albumin on in vitro activity.

Lipase activity was determined in gastric juice obtained from newborn babies who were fed formula milk (180 ml/kg/day). Samples of gastric juice collected 3 h after a feed were pooled and incubated with bovine serum albumin (BSA). The incubation mixtures containing milk fatty acids (750 nmol/tube) and BSA (0-5%) showed maximal lipase activity (as measured by the liberation of radiolabelled fatty acid from radiolabelled triglyceride) with 1.87% BSA in the first 60 min, but at subsequent time intervals higher enzyme activities were observed with 2.5 and 5% BSA. After extracting milk fatty acids from gastric juice the effects of BSA and sodium oleate on lipase activity were studied. The addition of BSA appeared to inhibit the enzyme, but when sodium oleate was included in the incubating system there was either stimulation or inhibition of lipase activity. A dual effect of BSA (i.e. stimulatory or inhibitory) was observed depending on the relative amounts of BSA and fatty acid present in the incubation tube. It is suggested that 1.87-5% is the optimum concentration range of BSA for the determination of lipase activity in gastric juice, in the presence of 250-500 nmol of fatty acid.