Lipase Units Research Articles

Hydrolysis of Fatty Acid Esters of Acetaminophen in Buffered Pancreatic Lipase Systems I

A series of fatty acid esters of acetaminophen were prepared beginning with the acetate, the propionate, and all even‐numbered fatty acids and going through the octadecanoate. The enzymatic hydrolysis of all derivatives was studied in vitro with varying amounts of lipase added to the hydrolysis mixtures. Under the conditions of the in vitro hydrolysis, it was observed that all derivatives were hydrolyzed more readily in an aqueous medium at pH 7.8. A positive relationship was seen between the hydrolysis rates and the concentration of lipase at this pH. There was a negative relationship between the chain length of the acyl moiety and the corresponding hydrolysis rates. The short chain esters were hydrolyzed at rates many times more rapid than the long chain esters. The intermediate chain‐length esters, p‐acetamidophenyl de‐canoate, p‐acetamidophenyl laurate, and p‐acetamidophenyl my‐ristate, were hydrolyzed at intermediate time periods extending over 12 hr, approaching completion at 97.5, 87.5, and 80.5%, respectively, when 18 Wilson units of lipase was used in each milliliter of hydrolysis mixture. The longer chain esters, p‐acetamidophenyl palmitate and p‐acetamidophenyl stearate, were hydrolyzed to the extent of 16 and 8%, respectively, over 12 hr under the same in vitro conditions

The metabolism of free fatty acids and chylomicron triglyceride fatty acids by isolated rat liver cells

1. 1. A study of the uptake and metabolism of chylomicron triglyceride fatty acids and free fatty acids has been carried out in a preparation of morphologically intact isolated liver cells from fasted rats. Cells incubated with chylomicrons in the presence of serum did not take up significant amounts of [ 14C]triglyceride fatty acids and oxidized less than 1% to 14CO 2 and [ 14C]Ketone bodies. When cells were incubated in the absence of serum, the recovery of 14C in the liver lipids was increased 90-fold but oxidation to 14CO 2 and [ 14C]ketone bodies was not significantly increased. These results indicate that the presence of serum in the incubation prevents adherence of chylomicrons to cell surfaces. 2. 2. Significant oxidation of [ 14C]triglyceride fatty acids to 14CO 2 and [ 14C]ketone bodies was observed only when lipoprotein lipase was added to the incubation. When 13 units of lipoprotein lipase were added to the incubation, the recoveries of [ 14C]triglyceride fatty acids in oxidation products were similar to recoveries from [ 14C]free fatty acids. 3. 3. These experiments strengthen the hypothesis that triglycerides are not taken up or metabolized by liver parenchymal cells in amounts that are physiologically significant. Triglycerides are probably metabolized by hydrolysis by lipoprotein lipase in peripheral capillary beds. The reaction products, glycerol and free fatty acids, may then recirculate to the liver in which form they readily cross the liver cell membrane.

Effect of Lipid Materials on the Production of Lipase by Torulopsis ernobii

The yeast Torulopsis ernobii produced approximately 50 units of extracellular lipase (glycerol ester hydrolase, E.C. 3.1.1.3) per ml when grown in 30-liter fermentors at 33 C for 40 hr in a base medium at p H 5.0. The addition of fats, oils, triglycerides, or higher fatty acids to this medium at concentrations of 0.2 to 0.6% markedly increased production; twofold increases in yield were obtained when 0.2% olive oil or a mixture of 0.14% oleic acid and 0.04% palmitic acid was added. The production of lipase paralleled growth, and the role of lipid materials in augmenting lipase production appears to be related to cell growth.

Effect of Lipid Materials on the Production of Lipase by Torulopsis ernobii

The yeast Torulopsis ernobii produced approximately 50 units of extracellular lipase (glycerol ester hydrolase, E.C. 3.1.1.3) per ml when grown in 30-liter fermentors at 33 C for 40 hr in a base medium at pH 5.0. The addition of fats, oils, triglycerides, or higher fatty acids to this medium at concentrations of 0.2 to 0.6% markedly increased production; twofold increases in yield were obtained when 0.2% olive oil or a mixture of 0.14% oleic acid and 0.04% palmitic acid was added. The production of lipase paralleled growth, and the role of lipid materials in augmenting lipase production appears to be related to cell growth.

Development of a clinically useful colorimetric method for serum lipase

<h2>Summary</h2> Sodium cholate has proved to be a more reliable activator of human pancreatic lipase in human serum than the unsatisfactory sodium taurocholate, which has been useful in the measurement of dog serum lipase. Since both activators work well on human pancreas alone, human serum plays a role in determining the ability to detect human pancreatic lipase with either activator. A method for the determination of human serum lipase which takes advantage of this species difference has been developed. This new method utilizes well buffered sodium cholate as a reliable activator and β-naphthyl myristate as a substrate. The advantage of the myristate over the laurate ester of β-naphtyl is the slower rate of hydrolysis of the former by serum esterase. As little as 0.2 μg. of a pooled extract of human pancreas added to 0.2 ml. of human serum can be detected. Lipase activity can be demonstrated in normal human serum, with an upper limit of 265 Klett units or 75 lipase units, and with a mean of 155 Klett units or 43 lipase units. A survey of serum lipase in patients suspected of having pancreatitis was performed using a one hour and a five hour incubation method. Elevation of both lipase and amylase activity in serum correlated with the presence of early acute pancreatitis. Although correlation with amylase activity was closer, false positive <i>amylase</i>activity was detected in some patients by means of the lipase assay. Marked elevations in amylase were almost always accompanied by elevations in lipase. Although the five hour test is more reliable, the one hour test may serve as a useful adjunct in emergencies, since a positive one hour test consistently predicted a positive five hour test.

Photometric Microdetermination of Serum Lipase with a Phenyl Laurate Substrate

Abstract The Raderecht and Moskau procedure for pancreatic lipase (6) has been modified for determining the small amounts of this enzyme present in normal blood serum. The present investigation confirmed their findings: that phenyl laurate provides a stable easily-prepared substrate of uniform composition; that the substrate is specifically split by serum and pancreatic lipase; and that the reaction product (phenol) can be readily determined by a simple and sensitive colorimetric procedure. The lipase units are expressed in the same manner as are phosphatase units; i.e., milligrams of phenol liberated per 100 ml. serum at 370° in 30 min. The normal range, based on 40 sera, was found to be 2.5-5.6 units. The serum lipase values were shown to be significantly elevated in a number of cases with acute pancreatic disease. The advantage of this procedure over others presently employed for diagnostic evaluation of these conditions is discussed.