Kinetics of enzymatic hydrolysis of quaternary aminoalkyl esters of aromatic mono- and dicarboxylic acids by butyrylcholinesterase from horse serum]

Enzymatic hydrolysis kinetics of benzoylcholine (BzCh), phehylpropionic acid choline ester (PK-157), suberic acid dicholine ester (D-6) and p-phenylenediacetic (PK-139), p-phenylenedipropionic (PK-154 and PK-155), p-phenylenediacryc (PK-150 and PK-151) and phtalic (PK-105) acids diaminoalkyl esters by horse blood serum butyrylcholinesterase (BuChE) was studied. Hydrolysis constants Km, V and Kss were estimated by means of different graphic methods. PK-157 ester turned to be highly specific selective substrate for BuChE, its V being 20 times as high and Km -- 20 times as low as those for acetylcholine (ACh). The highest V value was found for D-6 in the case of diesters. Hydrolysis of aromatic dicarbonic acids diesters was characterized with significantly lower V values (0.6-10.% of V for ACh) and extremely low Km values (approximately 10(-5) -- 10(-6) M). Substrate inhibition was observed under the hydrolysis of BzCh, PK-157, D-6 and all aromatic dicarbonic acids esters by BuChE. Formal kinetic analysis revealed that inactive complex, which formed in this case, corresponded to ES2 composition. The appearance of substrate inhibition for BuChE and its increasing are supposed to be due to the increase in the size and in the rigidity of the acyl part of the molecule in the number of substrates studied.     

Rat butyrylcholinesterase-catalysed hydrolysis of N-alkyl homologues of benzoylcholine

The purpose of this work was to study the catalytic properties of rat butyrylcholinesterase with benzoylcholine (BzCh) and N-alkyl derivatives of BzCh (BCHn) as substrates. Complex hysteretic behaviour was observed in the approach to steady-state kinetics for each ester. Hysteresis consisted of a long lag phase with damped oscillation. The presence of a long lag phase, with no oscillations, in substrate hydrolysis by rat butyrylcholinesterase was also observed with N-methylindoxyl acetate as substrate. Hysteretic behaviour was explained by the existence of two interconvertible butyrylcholinesterase forms in slow equilibrium, while just one of them is catalytically active. The damped oscillations were explained by the existence of different substrate conformational states and/or aggregates (micelles) in slow equilibrium. Different substrate conformational states were confirmed by 1H-NMR. The K(m) values for substrates decreased as the length of the alkyl chain increased. High affinity of the enzyme for the longest alkyl chain length substrates was explained by multiple hydrophobic interactions of the alkyl chain with amino acid residues lining the active site gorge. Molecular modelling studies supported this interpretation; docking energy decreased as the length of the alkyl chain increased. The long-chain substrates had reduced k(cat) values. Docking studies showed that long-chain substrates were not optimally oriented in the active site for catalysis, thus explaining the slow rate of hydrolysis. The hydrolytic rate of BCH12 and longer alkyl chain esters vs. substrate concentration showed a premature plateau far below V(max). This was due to the loss of substrate availability. The best substrates for rat butyrylcholinesterase were short alkyl homologues, BzCh - BCH4.     

Significance of lipoidal estradiol in human mammary tumors

Incubations of p-nitrophenyl fatty acyl esters and estradiol-17 beta fatty acyl 17-esters with porcine esterase, human mammary tumor cytosol and rat uterine cytosol leads to ester hydrolysis of compounds with short chain fatty acids. Esters with long chain fatty acids show no hydrolysis except in the presence of Tween 80. Short chain fatty acid esters have a higher binding potency to the estrogen receptor than long chain fatty acid esters. Extraction of the nuclear receptor peak sedimenting at 4.6S and identification of the steroid showed that about 90% of the radioactivity was associated with estradiol and only 10% with estradiol esters. These studies show that estradiol fatty acyl esters act as a storage form from which estradiol is released by enzymatic hydrolysis.     

Long-acting contraceptive agents: in vitro hydrolysis of esters of norethisterone and levonorgestrel

The hydrolysis of 108 esters of norethisterone (17 alpha-ethynyl-17 beta-hydroxyestr-4-en-3-one) was studied in vitro using a rabbit liver preparation. Introduction of a double or triple bond into a straight-chain ester did not inhibit hydrolysis but a marked reduction in hydrolysis was produced on replacement of a methylene group by an oxygen atom. Hydrolysis was inhibited by substituents at C2 of the ester chain except in short chain esters. Cyclopropylcarboxylate and cyclobutylcarboxylate were readily hydrolysed and introduction of a furan ring into the side-chain did not affect hydrolysis. No hydrolysis occurred with a cholesteryl carbonate ester or with a pentamethyldisilyloxy ether. Forty-nine esters of levonorgestrel (13 beta-ethyl-17 alpha-ethynyl-17 beta-hydroxygon-4-en-3-one) were also studied. In general, the pattern of hydrolysis for these esters was similar to that of the norethisterone esters. However, with few exceptions the levonorgestrel esters were hydrolyzed more slowly. For those esters for which information regarding the biological activity was available, there was no correlation between the potency of the esters and their rate of hydrolysis in vitro.     

Calcineurin-catalyzed reaction with phosphite and phosphate esters of tyrosine.

A convenient synthesis is reported for the preparation of the phosphite ester of tyrosine methyl ester. By use of calcineurin, at 30 degrees C, a phosphite ester was hydrolyzed with a VM value [119 nmol/(min.micrograms of E)] approximately 500 times greater than that obtained with tyrosine phosphate [0.23 nmol/(min.microgram of E)] as substrate, but with similar KM values (12 mM for Tyr-PH ME, 11 mM for Tyr-P). Acid phosphatase, on the other hand, hydrolyzed the phosphite ester with a VM and KM value lower than those obtained with tyrosyl phosphate. The temperature dependence of the kinetic parameters (KM and VM) was evaluated, and the activation parameters were obtained with both substrates. The entropy of activation associated with the enzymatic hydrolysis of tyrosine phosphate agrees with the entrophy change for the hydrolysis of the monoanion of phosphate monoesters. The energy of activation for both substrates was in agreement with the energy change for hydrolysis of the oxygen-phosphorous linkage of phosphate monoester monoanions and phosphite esters. These results are consistent with a scheme of general acid catalysis in the action of calcineurin.     

alpha,beta-Dehydrophenylalanine choline esters, a new class of reversible inhibitors of human acetylcholinesterase and butyrylcholinesterase

Our goal was to design, synthesize, and evaluate new cholinesterase inhibitors. Fourteen dehydroamino acids esterified to choline and to its ternary analog were synthesized by a new method that gave a yield of 84-93%. The potency of the amino acid ester derivatives was tested by measuring K(i) values for inhibition of human red cell acetylcholinesterase and human plasma butyrylcholinesterase. The most potent compound was a choline ester of dehydrophenylalanine where the amine group of the amino acid was derivatized with a benzoyl group containing a methoxy in the 2-position, CH(3)O(C(6)H(4))CONHC(CHC(6)H(5))COOCH(2)CH(2)N(+)(CH(3))(3). This compound was a strong inhibitor of both human acetylcholinesterase and human butyrylcholinesterase, with K(i) values of 10 microM and 0.08 microM, respectively. These K(i) values are comparable to that of Rivastigmine. Docking of the most potent compound into the active site of human butyrylcholinesterase showed that the lowest energy model had two benzene rings oriented towards Trp 82 and Tyr 332 whereas the positively charged nitrogen group was stabilized by Trp 231. This orientation placed the ester group 3.89 A from the active site Ser 198, a distance too far for covalent bonding, explaining why the esters are inhibitors rather than substrates. This class of anticholinesterase agents has the potential for therapeutic utility in the treatment of disorders of the cholinergic system.     

Comparison of mesophilic and thermophilic feruloyl esterases: characterization of their substrate specificity for methyl phenylalkanoates

The active sites of feruloyl esterases from mesophilic and thermophilic sources were probed using methyl esters of phenylalkanoic acids. Only 13 out of 26 substrates tested were significant substrates for all the enzymes. Lengthening or shortening the aliphatic side chain while maintaining the same aromatic substitutions completely abolished activity for both enzymes, which demonstrates the importance of the correct distance between the aromatic group and the ester bond. Maintaining the phenylpropanoate structure but altering the substitutions of the aromatic ring demonstrated that the type-A esterase from the mesophilic fungus Fusarium oxysporum (FoFaeA) showed a preference for methoxylated substrates, in contrast to the type-B esterase from the same source (FoFaeB) and the thermophilic type-B (StFaeB) and type-C (StFaeC) from Sporotrichum thermophile, which preferred hydroxylated substrates. All four esterases hydrolyzed short chain aliphatic acid (C2-C4) esters of p-nitrophenol, but not the C12 ester of laurate. All the feruloyl esterases were able to release ferulic acid from the plant cell wall material in conjunction with a xylanase, but only the type-A esterase FoFaeA was effective in releasing the 5,5' form of diferulic acid. The thermophilic type-B esterase had a lower catalytic efficiency than its mesophilic counterpart, but released more ferulic acid from plant cell walls.     

Esterolytic and proteolytic enzymes of the rat adenohypophysis

Summary Characteristics of the hydrolysis of histochemical substrates 5-bromoindoxyl acetate, naphthyl acetate, proprionate, butyrate, caprylate, laurate, myristate, and palmitate, acetyl and butyryl thiocholhie, chloroacetyl and trifluoroacetyl -naphthylamide, benzoyl-arginine -naphthylamide and proteinase substrates human hemoglobin and glycyl-phenylalanine amide by the rat pituitary tissue homogenate and DEAE-cellulose chromatography fractions were determined.In DEAE-cellulose chromatography fractions four separate activities were found splitting short and long chain carboxylic esters. The activity hydrolysing most rapidly 5-bromoindoxyl acetate was resistant to E 600 and was identified as C esterase. Three of the remaining esterase activities were sensitive to E 600 and two of them hydrolysed more rapidly short-chain fatty acid esters while one preferred long-chain fatty acid esters as substrate.One peak of activity was identified as nonspecific cholinesterase on the basis of inhibition studies and hydrolysis of thiocholine substrates. Chloroacetyl -naphthylamide was hydrolysed minimally. Hydrolysis of trifluoroacetyl -naphthylamide was ascribed to E 600 resistant enzyme with pH-optimum at 8.3 hydrolysing also the thiocholine substrates and slowly long-chain fatty acid esters.Five different proteinases hydrolysing human hemoglobin were separated, three of them with pH-optima on the acid and two on the alkaline side of pH. The activities hydrolysing benzoyl-arginine naphthylamide were cysteine activated and had pH-optima around 5.3. None of the peaks of the proteinase activities appeared to coinside with the hydrolysis peaks of any of the histochemical ester substrates in the DEAE fractions.     

Human plasma carboxyl esterase-catalyzed triolein hydrolysis. Existence of promoting factor in serum

The possibility that some factor in serum changes the substrate specificity of purified human plasma carboxyl esterase, which hydrolyzes the short chain fatty acid ester, tributyrin, was investigated. The purified carboxyl esterase from human plasma hydrolyzed 48 mmol of tributyrin/mg of protein/h, monoolein at 1560 mumol of released fatty acids/mg of protein/h, diolein at 133 mumol of released fatty acids/mg of protein/h, and triolein at less than 10 mumol of released fatty acids/mg of protein/h. When human serum was applied to phenyl-Sepharose, a triolein hydrolysis-promoting factor (THPF) for purified carboxyl esterase was bound to the gel and was eluted with water. This partially purified human serum THPF enhanced carboxyl esterase-catalyzed triolein hydrolysis about 30-fold, diolein hydrolysis 2-fold, and monoolein hydrolysis 1.5-fold. Hydrolysis of triolein in very low density lipoproteins (d less than 1.006) and intermediate lipoproteins (1.006 less than d less than 1.019) by carboxyl esterase was also enhanced by addition of THPF. THPF activity was reduced by treatment of delipidation, but resistant to trypsin treatment or heating at 50 degrees C. These results indicated that serum carboxyl esterase can hydrolyze the long chain fatty acid ester, triolein, in the presence of triolein hydrolysis-promoting factor in serum.     

Study of hydrolysis of aminoalcohol ethers, phenol and choline under the action of horse blood serum cholinesterase]

Hydrolysis of ethers of saturated and unsaturated alcohols and ethers, e.g. phenol and choline, under the action of horse blood serum cholinesterase, was studied. The reactivity towards enzymatic hydrolysis is decreased due to a greater length of the chain in the alcohol residue of the benzoic acid aminoethers; at nCH2 = 4 the compound is a poor substrate. An increase in nydrophobicity of the acyl residue of the ether molecule also leads to a decrease in the Vmax and Km values. In case of cholinesterase substrates, an increase in the molecule hydrophobicity results in an increase of its non-productive absorption on the active surface of the enzyme, which decreases its hydrolysis. Aminobutynol benzoates are hydrolyzed by cholinesterase more rapidly as compared to the ethers of corresponding aminobutanols and their homologs.     

The substrate requirements of phospholipase D

The hydrolysis rates of different diphosphates, compared with the one observed with natural phosphatidylcholine, are used to identify the molecular basis for phospholipase D (PLD) catalysis. Experimental data strongly support the idea that PLD is a rather generic phosphodiesterase with very wide substrate specificity and a net preference for lipophilic substrates. The presence of choline in the polar head is not required for activity although it improves hydrolysis efficiency. Choline esters are found to be substrates for PLD hydrolysis, but only with long chain fatty acids.     

Bacillus cereus phospholipase C: carboxylic acid ester specificity and stereoselectivity

Thiophosphate analogs of phosphatidylcholine have been synthesized with varying structural complexity. These analogs have been used in a continuous spectrophotometric assay for phospholipase C (Bacillus cereus) to estimate the minimal structural requirements associated with the non-polar portion of the substrate phospholipid. The analogs were of three types containing zero, one or two carboxylic acid ester functionalities. The analogs with one or two ester groups acted as substrates for phospholipase C, while those without an ester functionality were not hydrolyzed. The rac-phosphatidylcholine analog with two ester functionalities gave biphasic time-course results, and was subsequently resolved into enantiomers by selective hydrolysis with a sterospecific phospholipase A2 (Crotalus atrox). The enantiomer with R absolute configuration was rapidly hydrolyzed by the phospholipase C while the enantiomer with the S configuration was slowly hydrolyzed after a long induction period. The results suggest that the B. cereus phospholipase C is specific for an ester functionality and is stereoselective for the R absolute configuration at glycerol C-2.     

A subunit-sized butyrylcholinesterase present in high concentrations in pooled rabbit serum

A butyrylcholinesterase of mol.wt. approx. 83000 was observed in pooled rabbit serum. The enzyme was named monomeric butyrylcholinesterase to distinguish it from the larger oligomeric butyrylcholinesterase of horse and human serum whose subunits are the same size as the monomeric enzyme. The active-site concentration of monomeric butyrylcholinesterase in the pooled serum was 0.18mum, which is five times the concentration of butyrylcholinesterase in pooled horse serum. This was surprising, since the horse serum is regarded as a rich source of butyrylcholinesterase, whereas rabbit serum is not generally thought to contain significant amounts of any butyrylcholinesterase. The explanation, in large part, was the relatively low k(cat.) of the monomeric enzyme, which was approx. 57s(-1) with butyrylthiocholine as substrate and is one-thirtieth of the comparable k(cat.) of horse butyrylcholinesterase. The substrate specificity of monomeric butyrylcholinesterase also differed significantly from that of horse and human butyrylcholinesterase. For example, with the monomeric enzyme, the hydrolysis of 1mm-acetylthiocholine was only 4% the rate for 1mm-butyrylthiocholine, whereas human and horse butyrylcholinesterases hydrolysed 1mm-acetylthiocholine at 50% of the rate for 1mm-butyrylthiocholine. Moreover, monomeric butyrylcholinesterase generally hydrolysed aromatic esters more rapidly than choline esters, whereas the reverse is true of the butyrylcholinesterases. To facilitate the study of monomeric butyrylcholinesterase, it was separated from the larger butyrylcholinesterase and acetylcholinesterase, also present in rabbit serum, and purified 89-fold by fractionation with (NH(4))(2)SO(4) and ion-exchange chromatography.     

Evaluation of nitrate-substituted pseudocholine esters of aspirin as potential nitro-aspirins

Herein we explore some designs for nitro-aspirins, compounds potentially capable of releasing both aspirin and nitric oxide in vivo. A series of nitrate-bearing alkyl esters of aspirin were prepared based on the choline ester template preferred by human plasma butyrylcholinesterase. The degradation kinetics of the compounds were followed in human plasma solution. All compounds underwent hydrolysis rapidly (t(1/2) approximately 1min) but generating exclusively the corresponding nitro-salicylate. The one exception, an N-propyl, N-nitroxyethyl aminoethanol ester produced 9.2% aspirin in molar terms indicating that the nitro-aspirin objective is probably achievable if due cognisance can be paid to the demands of the activating enzyme. Even at this low level of aspirin release, this compound is the most successful nitro-aspirin reported to date in the key human plasma model.     

Kinetics of hydrolysis of phenylthiazolones of arginine, homoarginine, norarginine, and canaavanine by trypsin.

Phenylthiazolones (PTAs) of arginine and its homologs and analogs, homoarginine, norarginine (alpha-amino-gamma-guanidinobutyric acid), canavanine, and gamma-hydroxyarginine, were prepared. A steady-state kinetic analysis of the trypsin [EC 3.4.21.4]-catalyzed hydrolysis reactions was carried out and the kinetic parameters for these internal thioesters were compared with those for normal linear ester substrates. PTA-gamma-hydroxyarginine was so labile that hydrolysis by the enzyme could not be followed. PTA-arginine has a specificity constant (Kcat/Km) comparable to that for the Nalpha-unblocked arginine ester substrate, though the value is about 0.1% of that for a specific ester substrate, Nalpha-tosylarginine methyl ester. PTA derivatives of canavanine and homoarginine were hydrolyzed with Kcat/Km walues of the same order of magnitude as that for PTA-arginine. However, PTA-noraginine was much less susceptible to tryptic hydrolysis that PTA-homoarginine, while the linear esters of norarginine are known to be more susceptible than those of homoarginine.     

Carnitine and carnitine esters in rat bile and human duodenal fluid

The recent discovery of carnitine and its esters in rat bile has led to much speculation about its role. The objectives of these studies were to investigate the origin of carnitine esters in rat bile and to study the presence of carnitine in human bile-rich duodenal fluid. Bile was collected from chow-fed (n = 11), fasted (72 h, n = 6), and fasted plus 2-tetradecylglycidic acid administered (72 h, n = 5) male adult rats under sodium pentobarbital anaesthesia. Carnitine and carnitine ester content was measured in the bile and compared with serum and liver carnitine. Bile from fed rats was found to contain 80% acylcarnitine, one-third of this as long chain carnitine esters. Fasting caused no change in the secretion rate of acylcarnitine into the bile, although long chain carnitine ester secretion almost doubled. Conversely, 2-tetradecylglycidic acid treatment caused a decrease in long chain carnitine ester secretion into bile. Duodenal fluid was collected from patients with suspected cholelithiasis (n = 10) before and after pancreozymin-cholecystokinin injection. Although carnitine concentration was variable, it was consistently 80% esterified. These data associate bile carnitine with hepatic carnitine metabolism and establish the presence of carnitine and carnitine esters in the human intestinal lumen.     

Role of lysosomal acid lipase in the metabolism of plasma low density lipoprotein. Observations in cultured fibroblasts from a patient with cholesteryl ester storage disease.

The hydrolysis of cholesteryl esters contained in plasma low density lipoprotein was reduced in cultured fibroblasts derived from a patient with cholesteryl ester storage disease, an inborn error of metabolism in which lysosomal acid lipase activity is deficient. While these mutant cells showed a normal ability to bind low density lipoprotein at its high affinity cell surface receptor site, to take up the bound lipoprotein through endocytosis, and to hydrolyze the protein component of the lipoprotein in lysosomes, their defective lysosomal hydrolysis of the cholesteryl ester component of the lipoprotein led to the accumulation within the cell of unhydrolyzed cholesteryl esters, the fatty acid distribution of which resembled that of plasma lipoprotein. When the cholesteryl ester storage disease cells were incubated with low density lipoprotein, the reduced rate of liberation of free cholesterol by these mutant cells was associated with a delay in the occurrence of two lipoprotein-mediated regulatory events, suppression of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity, and activation of endogenous cholesteryl ester formation. In contrast to their defective hydrolysis of exogenously derived lipoprotein-bound cholesteryl esters, the choleseryl ester storage disease cells showed a normal rate of hydrolysis of cholesteryl esters that had been synthesized within the cell. These data lend support to the concept that in cultured human fibroblasts cholesteryl esters entering the cell bound to low density lipoprotein are hydrolyzed within the lysosome and that one of the functions of this intracellular organelle is to supply the cell with free cholesterol.     

Influence of the amino acid moiety on deconjugation of bile acid amidates by cholylglycine hydrolase or human fecal cultures

The influence of the chemical structure of the amino acid (or amino acid analogue) moiety of a number of synthetic cholyl amidates on deconjugation by cholylglycine hydrolase from Clostridium perfringens was studied in vitro at pH 5.4. Conjugates with alkyl homologues of glycine were hydrolyzed more slowly as the number of methylene units increased (cholylglycine greater than cholyl-beta-alanine greater than cholyl-gamma-aminobutyrate). In contrast, for conjugates with the alkyl homologues of taurine, cholylaminopropane sulfonate was hydrolyzed slightly faster than cholyltaurine, whereas cholylaminomethane sulfonate was hydrolyzed much more slowly. When glycine was replaced by other neutral alpha-amino acids, rates of hydrolysis decreased with increasing steric hindrance near the amide bond (cholyl-L-alpha-alanine much much greater than cholyl-L-leucine much greater than cholyl-L-valine greater than cholyl-L-tyrosine much greater than cholyl-D-valine). Conjugation with acidic or basic amino acids also greatly reduced the rates of hydrolysis, as cholyl-L-aspartate, cholyl-L-cysteate, cholyl-L-lysine, and cholyl-L-histidine were all hydrolyzed at a rate less than one-tenth that of cholylglycine. Methyl esterification of the carboxylic group of the amino acid moiety reduced the hydrolysis, but such substrates (cholylglycine methyl ester and cholyl-beta-alanine methyl ester) were completely hydrolyzed after overnight incubation with excess of enzyme. In contrast, cholyl-cholamine was not hydrolyzed at all, suggesting that a negative charge at the end of the side chain is required for optimal hydrolysis. Despite the lack of specificity for the amino acid moiety, a bile salt moiety was required, as the cholylglycine hydrolase did not display general carboxypeptidase activity for other non-bile acid substrates containing a terminal amide bond: hippuryl-L-phenylalanine and hippuryl-L-arginine, as well as oleyltaurine and oleylglycine, were not hydrolyzed. Fecal bacterial cultures from healthy volunteers also hydrolyzed cholyl-L-valine and cholyl-D-valine more slowly than cholylglycine, suggesting that cholylglycine hydrolase from Clostridium perfringens has a substrate specificity similar to that of the deconjugating enzymes of the fecal flora. The results indicate that modification of the position of the amide bond, introduction of steric hindrance near the amide bond, or loss of a negative charge on the terminal group of the amino acid moiety of the bile acid conjugate greatly reduces the rate of bacterial deconjugation in vitro when compared to that of the naturally occurring glycine and taurine conjugates.     

Lipolysis of menhaden oil triacylglycerols and the corresponding fatty acid alkyl esters by pancreatic lipase in vitro: a reexamination

In order to distinguish between possible fatty acid differences during lumenal lipolysis and cellular absorption, we have reinvestigated the in vitro hydrolysis of menhaden oil and its alkyl esters by pancreatic lipase. For this purpose we incubated menhaden oil or its fatty acid methyl and ethyl esters with porcine pancreatic lipase in the presence of bile salts and determined the composition of the released free fatty acids, monoacylglycerols, diacylglycerols, and residual triacylglycerols, or the free fatty acids and residual alkyl esters, respectively, by thin-layer and gas-liquid chromatography. There was significant discrimination against the delta 4- to delta 7-unsaturated fatty acids of both medium and long chain lengths during the hydrolysis of menhaden oil and its fatty acid ethyl esters. In general, the ethyl esters were hydrolyzed 10-50 times more slowly than the corresponding glyceryl esters, depending on the exact ratio of the two substrate types. None of the triacylglycerols or ethyl esters, however, was completely resistant to hydrolysis resulting in an eventual cleavage of all the alkyl esters and presumably all the primary ester bonds in the triacylglycerol molecules. Since the rate of release of the least resistant fatty acid exceeded that of the most resistant acid by only a factor of 6, it is concluded that in the presence of a large excess of lipase the liberated fatty acids would approach the composition of the dietary alkyl or glyceryl esters, as observed during lumenal lipolysis (Yang, L.-Y., A. Kuksis, and J. J. Myher. 1989. Biochem. Cell Biol. 67: 192-204).     

Effect of substrate composition and concentration on aortic cholesterol ester hydrolase activity.

Cholesterol ester hydrolase activity of pig aorta has been examined under optimum experimental conditions for hydrolysis of different cholesterol esters. The enzyme specific activity values were in the numerical order of substrates hydrolyzed: cholesteryl linoleate larger than or equal to linolenate greater than palmitate larger than or equal to stearate greater than oleate. The results are discussed in relation to the arterial accumulation of cholesterol esters.