Horse esterase

Diol bonded silica Glucosamine, bovine serum albumin, immunoglobulin, acetylcholine esterase, horse liver alcohol dehydrogenase [136]... 

By a careful fractionation of normal horse serum, involving as an essential part of the process a separation of closely related substances by the Schtitz168 foam technique, Bader, Schiitz and Stacey16 obtained a crystalline mucoprotein with high choline esterase activity. This appears to be the first mucoprotein obtained without the use of heat or alcohol, and while it is not yet claimed that the crystalline material is indeed the enzyme itself, arguments are advanced to show that the enzymic activity is closely bound up with mucoprotein structure. 

There is some confusion in the literature regarding the substances designated as anti-choline-esterases (usually shortened to anticholinesterases). The term cholinesterase was first used1 in connexion with an enzyme present in the blood serum of the horse which catalysed the hydrolysis of acetylcholine and of butyrylcholine, but exhibited little activity towards methyl butyrate,... 

The enzymes used by these workers were cholinesterase, prepared from horse serum, and horse-liver esterase. Parallel experiments were carried out with twice crystallized ovalbumin, and with an aged, dialysed specimen of horse serum with negligible esterase activity. 

R. I. Feldman, H. Weiner, Horse Liver Aldehyde Dehydrogenase. II. Kinetics and Mechanistic Implications of Dehydrogenase and Esterase Activity , J. Biol. Chem. 1972, 247, 267-272. 

E. Guibe-Jampel, G. Rousseau, L. Blanco, Enzymatic Resolution of Racemic Bicyclic Lactones by Horse Liver Esterase , Tetrahedron Lett. 1989, 30, 67-68. 

To test the selectivity of the self-screening process, six other enzymes belonging to the hydrolase family were tested under the same set of conditions as in DCL-A. These enzymes were butyrylcholinesterase, horse fiver esterase (HLE, EC 3.1.1.1), Candida cylindracea lipase (CCL, EC 3.1.1.3), (3-galactosidase ((3-Gal, EC 3.2.1.23), trypsin (EC 3.4.21.4), and... 

ROH, horse liver esterase, solid support (enantioselective)... 

Enantioselective enzymatic ester hydrolyses of prochiral trimethylsilyl-substituted diesters of the malonate type have been applied for the synthesis of the related optically active monoesters68. As an example of this particular type of biotransformation, the enantioselective conversion of the diester 82 is illustrated in Scheme 17. Hydrolysis of compound 82 in phosphate buffer, catalyzed by porcine liver esterase (PLE E.C. 3.1.1.1) or horse liver acetonic powder (HLAP), gave the optically active monoester 83 (absolute configuration not reported) in 86% and 49% yield, respectively. The enantiomeric purities... 

Jansz, H.S., Posthumus, C.H., Cohen, J.A. (1959). On the active site of horse-liver ali esterase. Biochim. Biophys. Acta 33 387-403. 

An interesting application of the esterase activity of horse liver acetone powder (HLE) has been the enantioselective hydrolysis of racemic lactones. The powder proved to be more effective than PLE in this hydrolysis, from which the unreacted lactone was recovered with high enantiomeric excess. The process seems more effective for S and medium size lactones (eq 13). ... 

Use Biochemical research, determination of phosphorus in insecticides and poisons. (2) Pseudo or nonspecific cholinesterase prepared from horse serum. This esterase hydrolyzes other esters, as well as choline esters. It occurs in blood serum, the pancreas, and the liver. 

By this time, esterases had been described in many animal tissues, and there seemed no reason to suppose that acetylcholine would be exceptionally resistant to their action. In 1932, Stedman et al. (S38) showed that liver esterases from the pig or cat were unable to catalyze the hydrolysis of acetylcholine, and a search was made for the enzyme responsible for the hydrolysis of this choline ester. They went on to describe and purify, for the first time, an enzyme present in horse serum which did catalyze the hydrolysis of acetylcholine. They called this enzyme choline-esterase, and this name—with or without the hyphen— has persisted. 

Main et al. (M5) found high concentrations of a butyrylcholine esterase, of relative molecular mass 83,000 daltons, in pooled rabbit serum. This was unexpected, since rabbit serum is classed with those mammalian sera that have low cholinesterase activities (A25, E2). Substrate specificity confirmed that the enzyme was a butyrylcholine esterase. Moreover, the active site concentration of the enzyme was five times that found for pooled horse serum, which is a rich source of the enzyme. The known fact that some rabbits can metabolize atropine, whereas others are unable to do so, can be explained by the presence or absence of serum atropinase, which is a genetic trait. Perhaps the subunit-sized butyrylcholine esterase is characteristic of some rabbits, but absent in others This seems probable according to Ellis (E9) and Koelle... 

K31), who found that benzoylcholinesterase activity varies widely among the sera of various rabbits. Unfortunately, the relevant genetics were not investigated. The presence of butyrylcholine esterase may also be questioned it acts—apparently—as a monomer in rabbit sera, but as a tetramer in human and horse sera. Perhaps the apparent absence of the tetramer and other polymers in some rabbits is the result of the inhibition or complete absence of an aggregating enzyme Does such an enzyme control the interconvertibility of the isoenzymes which are present in other plasma It is relevant that Main (private communication) isolated from rabbit liver cholinesterase two monomer forms of butyrylcholine esterase, one of which spontaneously formed a tetramer after purification. 

Table 11.1-5. Pig liver esterase-catalyzed enantiomer-differentiating hydrolysis of racemic carboxylic acid esters and lactones in aqueous solution (HLE horse liver esterase).

A large number of mono- and bicyclic lactones (73-91) have been obtained by using pig liver esterase in combination with horse liver esterase for the enantiomer-differentiating hydrolysis of the corresponding racemic lactones. Interestingly, in the series of methyl-substituted lactones (85-89), both enzymes show toward the seven-membered lactone (86) the opposite enantiomer selectivity as compared to the other lactones. 

Similarly, the respective dipeptide choline esters 34 are readily soluble in purely aqueous media (i. e. without added cosolvent) and are converted into the corresponding carboxylic acids under the mildest conditions, and without side attack on the peptide bonds and the N-terminal urethanes, by means of the commercially available butyrylcholine esterase from horse serum. The increased hydrophilicity of peptide choline esters was used advantageously used for the synthesis of peptides and very sensitive peptide conjugates such as lipidated peptides1118-1211, phosphorylated and glycosylated peptides158, 591 and nucleopeptides (Fig. 18-13)176, 781. 

Butyrylcholine esterase Origin horse serum Biozyme... 

Butyrylcholine Esterase Origin horse serum Fluka... 

Horse-serum cholinesterase Aged dialysed horse serum Ovalbumin Horse-liver esterase Heat-treated liver esterase Aged dialysed horse serum Ovalbumin... 

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