Studies on the substrate specificity of purified human milk lipoprotein lipase

Abstract

The fatty acid specificity of purified human milk lipoprotein lipase was studied using the C18 to C54 (total acyl carbon number) saturated and the C54 mono-, di- and triunsaturated monoacid triacylglycerols. Kinetic determinations indicated that the medium-chain triacylglycerols were better substrates than long- or very short-chain saturated triacylglycerols. The unsaturated triacylglycerols were hydrolyzed at rates comparable to that of tricaprylin with triolein having the highest rate of hydrolysis of the unsaturated species tested. The enzyme attacked the primary ester bond much more readily than the secondary ester bond. The purified human milk lipoprotein lipase showed a preferential stereospecific lipolysis of the sn-1-position of the triacylglycerol molecule.

Triacylglycerol metabolism by lymphocytes and the effect of triacylglycerols on lymphocyte proliferation

“…This suggests that the lymphocyte lipoprotein lipase has the ability to differentiate between substrates, possibly on the basis of both fatty acid chain length and degree of unsaturation. Although there are reports that lipoprotein lipase does not exhibit specificity with respect to the acyl chains of its substrate [39,40], the finding of greater hydrolysis of triacylglycerols containing PUFAs than of those containing saturated fatty acids is in accordance with a previous study of the substrate specificity of the enzyme from human milk [41]. That study showed that triacylglycerols containing linoleic or linolenic acids are hydrolysed at a rate up to four times greater than the rate of hydrolysis of triacylglycerols containing saturated fatty acids (myristic, palmitic or stearic acids) [41].…”

“…Although there are reports that lipoprotein lipase does not exhibit specificity with respect to the acyl chains of its substrate [39,40], the finding of greater hydrolysis of triacylglycerols containing PUFAs than of those containing saturated fatty acids is in accordance with a previous study of the substrate specificity of the enzyme from human milk [41]. That study showed that triacylglycerols containing linoleic or linolenic acids are hydrolysed at a rate up to four times greater than the rate of hydrolysis of triacylglycerols containing saturated fatty acids (myristic, palmitic or stearic acids) [41]. However, this earlier study found that triacylglycerol was the most rapidly hydrolysed triacylglycerol of those tested [41]; in the current study trioleoylglycerol was hydrolysed at a rate comparable with that of hydrolysis of triacylglycerols containing saturated fatty acids (Table 2).…”

“…That study showed that triacylglycerols containing linoleic or linolenic acids are hydrolysed at a rate up to four times greater than the rate of hydrolysis of triacylglycerols containing saturated fatty acids (myristic, palmitic or stearic acids) [41]. However, this earlier study found that triacylglycerol was the most rapidly hydrolysed triacylglycerol of those tested [41]; in the current study trioleoylglycerol was hydrolysed at a rate comparable with that of hydrolysis of triacylglycerols containing saturated fatty acids (Table 2).…”

“…However, lipoprotein lipase also exhibits specificity with respect to the position of fatty acid chains in the triacylglycerol, with the ester bond at position 1 being attacked in preference to that at position 2 [41]; this could make the interpretation of studies comparing rates ofhydrolysis of 'mixed' triacylglycerols difficult.…”

Incorporation of dietary triacylglycerols from olive oil and high-oleic sunflower oil into VLDL triacylglycerols of hypertensive patients

“…The enzyme is tightly regulated by the composition of dietary fats (Montalto & Bensadoun, 1993), can differentiate between substrates (Calder et al, 1994) and exhibits speci®city with respect to the position of fatty acid chains in the glycerol backbone (Wang et al, 1982). Accordingly, the composition of VLDL triacylglycerols appears to be a determinant for the conversion of VLDL into other lipoproteins and the uptake and metabolism of triacylglycerol metabolites by cells.…”