Substance Summary (SID 134224940) Intralipid is a brand name for the first safe fat emulsion for human use, approved in 1962 in Europe and invented by Professor Arvid Wretlind, Sweden. It is used as a component of parenteral nutrition for patients who are unable to get nutrition via an oral diet. It is an emulsion of soy bean oil, egg phospholipids (like LIPOVA-E120) and glycerin. Some lipids are potential substrates for digestive lipases.
A lipase was found to be present in dog stomach which appeared to be more abundant in the fundic than in the pyloric mucosa. Dog gastric lipase was extracted by soaking the gastric tissue and further purified after cation exchange, anion exchange and gel-filtration using fast protein liquid chromatography. The amino-acid composition, N-terminal amino-acid sequence, substrate specificity, interfacial and kinetic behavior and inactivation by sulfhydryl reagents were determined and compared with those of human and rabbit gastric lipases. We report for the first time that a gastric lipase is 13 times more active on long-chain than on short-chain triacylglycerols at pH 4.0, reaching a maximal specific activity of 950 U/mg on Intralipide emulsion.
Title: Purification, characterization and kinetic properties of the rabbit gastric lipase Moreau H, Gargouri Y, Lecat D, Junien JL, Verger R Ref: Biochimica & Biophysica Acta, 960:286, 1988 : PubMed
Rabbit gastric lipase was purified from an acetonic powder of rabbit stomach fundus. 25 mg of pure rabbit gastric lipase (glycerol ester hydrolase, EC 3.1.1.3) was obtained from 30 rabbit stomachs after ammonium sulfate fractionation, Sephadex G-100 gel filtration and cation exchange (mono S column) using a fast protein liquid chromatography (FPLC) system. The pure enzyme obtained was resistant to acidic pH conditions, and had specific activities of 1200, 850 and 280 U/mg, using, respectively, short- (tributyroylglycerol (TC4)), medium- (trioctanoyl- to tridecanoylglycerol (TC8-TC10)) and long-chain (soybean oil) triacylglycerols. The amino-acid composition was determined, and the first 30 N-terminal amino-acid residues were sequenced. Interfacial denaturation and catalytic properties on triacylglycerol emulsions were studied. Rabbit gastric lipase turned out to be structurally and kinetically very similar to human gastric lipase.
Under optimal conditions, assay for pure human gastric lipase was carried out with short- and long-chain triacylglycerol emulsions. Maximal specific activities of 1160 and 620 U/mg were obtained with tributyrin and soybean emulsion, respectively. We observed that with a tributyrin substrate, bovine serum albumin or bile salts must be added before the addition of the enzyme in order to prevent its irreversible interfacial denaturation. With long-chain triacylglycerols as substrate, a decrease with time in the rate of hydrolysis was associated with release of protonated long-chain fatty acids. The inhibitory effect of protonated fatty acids was also observed using tributyrin at pH 3.0. These observations support the conclusion that human gastric lipase shows no intrinsic specificity for short-chain triacylglycerols and that its apparent specificity is modulated by pH and presence of amphiphile in the incubation medium. Our conclusions support the view that, in the human, gastric lipolysis may play an important role in long-chain fat digestion.
