Carboxylesterases properties

Tsujita, T., and H. Okuda. 1983. Human liver carboxylesterase. Properties and comparison with human serum carboxylesterase. J Biochem 94 793. 

Imai T. Human carboxylesterase isozymes catalytic properties and rational drug design. Drug Metab Pharmacokinet 2006 21 (3) 173—185. 

Three isoenzymes of carboxylesterase were purified from rat liver micro-somes and were named RL1, RL2, and RH1. These differ from each other in their response to hormone treatment, inducibility, substrate specificity, and immunological properties [75], It was shown that RL1, RL2, and RH1 resemble hydrolases p/ 6.2/6.4, pI 6.0, and pI 5.6, respectively. Enzyme RL2 was found to be identical to egasyn, a protein with esterase activity found in the endoplasmic reticulum [76], The role of egasyn is to stabilize glucuronidase (EC 3.2.1.31) by noncovalent binding to the microsomal membrane. 

The intracellular localization of carboxylesterases is predominantly microsomal, the esterases being localized in the endoplasmic reticulum [73] [79] [93], They are either free in the lumen or loosely bound to the inner aspect of the membrane. The carboxylesterases in liver mitochondria are essentially identical to those of the microsomal fraction. In contrast, carboxylesterases of liver lysosomes are different, their isoelectric point being in the acidic range. Carboxylesterase activity is also found in the cytosolic fraction of liver and kidney. It has been suggested that cytosolic carboxylesterases are mere contaminants of the microsomal enzymes, but there is evidence that soluble esterases do not necessarily originate from the endoplasmic reticulum [94], In guinea pig liver, a specific cytosolic esterase has been identified that is capable of hydrolyzing acetylsalicylate and that differs from the microsomal enzyme. Also, microsomal and cytosolic enzymes have different electrophoretic properties [77]. Cytosolic and microsomal esterases in rat small intestinal mucosa are clearly different enzymes, since they hydrolyze rac-oxazepam acetate with opposite enantioselectivity [95], Consequently, studies of hydrolysis in hepatocytes reflect more closely the in vivo hepatic hydrolysis than subcellular fractions, since cytosolic and microsomal esterases can act in parallel. 

Thioesters play a paramount biochemical role in the metabolism of fatty acids and lipids. Indeed, fatty acyl-coenzyme A thioesters are pivotal in fatty acid anabolism and catabolism, in protein acylation, and in the synthesis of triacylglycerols, phospholipids and cholesterol esters [145], It is in these reactions that the peculiar reactivity of thioesters is of such significance. Many hydrolases, and mainly mitochondrial thiolester hydrolases (EC 3.1.2), are able to cleave thioesters. In addition, cholinesterases and carboxylesterases show some activity, but this is not a constant property of these enzymes since, for example, carboxylesterases from human monocytes were found to be inactive toward some endogenous thioesters [35] [146], In contrast, allococaine benzoyl thioester was found to be a good substrate of pig liver esterase, human and mouse butyrylcholinesterase, and mouse acetylcholinesterase [147],... 

Upadhya, G., Govardhan, L., and Veerabhadrappa, P. S. (1985). Purification and properties of a carboxylesterase from germinated finger millet (Eleusine coracana Gaertn.).. Biosci. 7, 289-301. 

Pancreatic cholesterol esterase (3.1.1.3.) aids in transporting cholesterol to the enterocyte. By utilizing a selective and potent cholesterol esterase inhibitor 6-chloro-3-(l-ethyl-2-cyclohexyl)-2-pyrone, the absorption of cholesterol in hamsters could be reduced [71]. Wadkins et al. [72] synthesized novel sulfonamide derivatives, which demonstrated greater than 200-fold selectivity for human intestinal carboxylesterase compared with the human liver carboxylesterase hCEl, and none of them was an inhibitor of human acetylcholinesterase or butyrylcholinester-ase. Maybe these agents can serve as lead compounds for the development of effective, selective carboxylesterase inhibitors for clinical applications. Also the potent P-gp inhibitor verapamil [73] as well as S,S,S-tributylphosphortrithionate (DEF) [74] may exhibit carboxylesterase inhibitory properties. Various other inhibitors of human esterases are listed in Table 5.6. 

Nishizawa M, Gomi H et al (1993) Purification and some properties of carboxylesterase from Arthrobacter globiformis, stereoselective hydrolysis of ethyl chrysanthemate. Biosci Biotech Biochem 57 594-598... 

Devonshire, A.L., The properties of a carboxylesterase from the peach-potato aphid, Myzuz persicae (Sulz.), and its role in conferring insecticide resistance, Biochem. J., 161, 675,1977. 

Quantitative Micro Complement Fixation Serologic Properties of Pig Liver Carboxylesterase... 

The pig liver carboxylesterase preparation and some of its physical properties have been described by Barker and Jencks. Antibodies to the carboxylesterase preparation were obtained by immunization of rabbits via the toe pads and muscles with 2 mg of enzyme emulsified in complete... 

Pig liver carboxylesterase (2 mg/ml) undergoes a decrease in sedimentation rate over a relatively narrow pH range (pH 4-5) that reflects dissociation of the whole molecule into subunits. The serologic activities of these whole and dissociated molecules are changed. Whereas 80% of the complement is fixed with the whole molecules, only about 20% is fixed with the dissociated molecules. Maximum complement fixation is stUl observed with about 0.05 ig of the dissociated protein. A decrease in complement fixing properties accompanies dissociation. 

Chahinian H, Ali YB, AbousaUiam A, Petty S, Mandrich L, Manco G, Canaan S, Sarda L (2005) Substrate specificity and kinetic properties of enzymes belonging to the hormone-sensitive lipase family comparison with non-lipolytic and lipolytic carboxylesterases. Biochim Biophys Acta 1738 29-36... 

Chahinian, H., and L. Sarda. 2009. Distinction between Esterases and Lipases Comparative Biochemical Properties of Sequence-Related Carboxylesterases. Protein Peptide Letters 16 (10) 1149-1161. 

Koller, E. Wolfbeis, O. S. Syntheses and spectral properties of longwave absorbing and fluorescing substrates for the direct and continuous kinetic assay of carboxylesterases, phosphatases, and sulfatases. Monatsh. Chem. 1985,116, 65-75. 

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