Abstract
The fatty acid specificity of the bile salt-activated lipase purified from human milk was studied using C12 to C54 (total acyl carbon) saturated and the C54 unsaturated triacylglycerols. Kinetic studies indicated that the short chain triacylglycerols were hydrolyzed more readily than the long chain triacylglycerols, and that the long chain unsaturated triacylglycerols were attacked more readily than the long chain saturated triacylglycerols. This fatty acid specificity was also apparent intramolecularly, both short chain and unsaturated fatty acids being released at higher rates than the saturated long chain acids. The enzyme possessed neither positional specificity nor stereospecificity as indicated by the nearly simultaneous appearance of the sn-1,2-, sn-2,3-, and sn-1,3-dioleoylglycerols from trioleoylglycerol. The hydrolyses of these three ester bonds were approximately at their anticipated chemical reactivities. Synthetic rac-1-monooleoylglycerols were hydrolyzed about 2 times faster than the sn-2-monooleoylglycerols. It is concluded that the bile salt-activated lipase may possess a special potential for a rapid release of short chain and polyunsaturated fatty acids from dietary triacylglycerols in the intestinal lumen of infants.
Highlights
The fatty acid specificity of the bile salt-activated release of lipolytic enzymes from pancreas does not seem t o lipase purified from human milwk as studied usingCIZ be adequate for fat digestionin early infancy
We wish to readily than the long chain triacylglycerols, and that communicate the results of studies on the positionaal nd fatty the long chain unsaturated triacylglycerols were at- acid specificityof this purified enzymeof human milk. tacked morereadily than the long chain saturatetdriacylglycerols
This fatty acid specificity was apparent intramolecularly, both short chain and rated fatty acids being released at higher rates tuhnasnatu-obtSauinbestdraftreosm-TChealbioracch-elm-p, aLlamiJtoolylal,2C-Aol, ewohylil-e3t-hseteraarco-yll-pglaylmceirtoowlya’lsthe saturated long chain acids
Summary
Incubation, two 0.1-ml aliquots each were taken from two separate incubation mixtures and combined with 0.9 ml of ice-cold heptane/. Startingwithanequimolarmixture (0.17 mM each triacylglycerol) of c12-c48 saturated triacylglycerols and trioleoylglycerol as substrates, the relative ratoefs lipolysis were measured by the relative disappearance of the various triacylglycerol species from the incubatiomn edium by means of high the positional specificity of hydrolysis was assayed with mixed acid temperature gas-liquid chromatography of the intact triacyltriacylglycerols by determining the release of the X-1,2- and X-1,3- glycerols. There was no the positional specificity of the enzyme was assayed by determining apparent hydrolysis of the c42-c54triacylglycerols under these the timecourse of release of different fatty acids from rac-l-palmitoyl- conditions. Intact triacylglycerols along with the mono- and diacylglycerols and free fatty acids released from the triacylglycerols during the enzyme digestion were determined by capillary gas chromatography using an 8-m-longopen tubular fused silica column coated with SE-54 The hydrolysis products were analyzed by high temperature capillary gas chromatography on a nonpolar column following trimethylsilylation of any mono- and diacylglycerols ( 1 8 )
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