Esterases specificity

Mendoza CE, Shields JB. 1971. Esterase specificity and sensitivity to organophosphorus and carbamate pesticides Factors affecting determination by thin layer chromatography. J Assoc Off Anal Chem 54 507-512. 

S. -H. Hung, L. Hedstrom, Converting trypsin to elastase substitution of the SI site and adjacent loops reconstitutes esterase specificity but not amidase activity, Prot. Eng. 1998, 11, 669-673. 

In vivo activity correlated with hydrolysis rates but no gross differences In esterase specificity were observed between dog serum and simulated intestinal fluid.Microbial transformations of clindamycin" and N-demethylclindamycin by Streptomyces species, in general, lead to prodrug forms of the parent antibiotics. 

Higa, H. H., Manzi, A., and Varki, A., 1989b, O-Acetylation and de-O-acetylation of sialic acids. Purification, characterization, and properties of a glycosylated rat liver esterase specific for 9-0-acetylated sialic acids, J. Biol. Chem. 264 19435-19442. 

Loewi and Navratil have shown that ACh can be enzymatically inactivated by heart extracts (69). This, however, is not surprising, since, as pointed out by Stedman, Stedman, and Easson (127), esterases are widely distributed in the animal organism and are known to hydrolyze a variety of esters. The important question was whether there is an enzyme which specifically hydrolyzes ACh. Stedman, Stedman, and Easson (l.c.) prepared from horse serum an enzyme which they considered to be an esterase specific for ACh and called it choline esterase. Later investigations do not support the assumption that the enzyme prepared by Stedman, et al. is really a specific choline esterase. There exists, however, an esterase which is specific for ACh. The specificity may be demonstrated by testing the action of an esterase on a number of substrates. In this way, a pattern may be obtained which makes it possible to distinguish the specific choline esterase from other esterases. The esterase in all nerve tissue is either exclusively or predominantly choline esterase. The enzyme is extremely stable. If kept at low temperature and at neutral pH, its activity remains unchanged for many months. The specificity of the enzyme as w eil as other properties will be discussed elsewhere (Nachmansohn and Rothenberg, 131 Nachmansohn, 102). 

Phosphonothioate Esters of Phenols. Phosphonates with a single P—C bond are highly toxic and persistent iasecticides but have not been used extensively because some compounds produce delayed neuropathy leading to irreversible paralysis ia higher animals, including humans. Such compounds specifically inhibit an enzyme, neurotoxic esterase, that is responsible for the growth and maintenance of long nerve axons (31,32). 

Specificity is not always perfect. Sometimes an enzyme will work with any member of a class of compounds. For example, some esterases (enzymes that catalyze the reaction of esters with water) will work with numerous esters of similar, but different, structures. Usually, in cases of this kind, one of the members of the substrate class will react faster than the others, so the rates will vary from one substrate to another. 

Ferri, S. R., and Meighen, E. A. (1991). A Lux-specific myristoyl transferase in luminescent bacteria related to eukaryotic serine esterases. J. Biol. Chem. 266 12852-12857. 

Lippi et. al (87) and Dirstine (88) circumvented titration by converting the liberated fatty acids into copper salts, which after extraction in chloroform are reacted with diethyldithio-carbamate to form a colored complex which is measured photometrically. While the end point appears to be more sensitive than the pH end point determination, the advantages are outweighed by the additional steps of solvent extraction, centrifugation and incomplete extraction when low concentrations of copper salts are present. Other substrates used for the measurement of lipase activity have been tributyrin ( ), phenyl laurate (90), p-nit ro-pheny1-stearate and 3-naphthyl laurate (91). It has been shown that these substrates are hydrolyzed by esterases and thus lack specificity for lipase. Studies on patients with pancreatitis indicate olive oil emulsion is definitely superior to water soluble esters as substrates for measuring serum lipase activity. 

As an accessory enzyme for the RGases, rhamnogalacturonan acetyl esterase (RGAE) was discovered in the same A. aculeatus preparation. This enzyme appeared to be specific for the de-acetylation of MHR and essential for the degradation of MHR by RGases A and B. 

The same enzyme (RGAE) could be purified from A. niger, together with two other esterases a feruloyl esterase (FAE) and an acetyl esterase (PAE) specific for the removal of one type of acetyl group present in the smooth regions of sugar-beet pectin. 

Each fruit has specific quantities and ratio of pectin, hemicelluloses and cellulose. These polysaccharides are important concerning enzymes activities required to produce juices and concentrates. Moreover, even if molecular weight and methylation degree of the pectin are specific for each fruit, during the fruit maturation, endogenous pectinases depolymerases and esterase are changing the pectin characteristics This broad variability of raw material makes difficult the standardisation of fruits processing. 

Enzymic release of ferulic acid from sugar beet pulp using a specific esterase from Aspergillus niger... 

Acetyl esterases with different specificity occur in one Aspergillus niger preparation. Three acetyl esterases were purified and characterised pectin acetyl esterase (PAE), feruloyl acetyl esterase (FAE) and rhamnogalacturonan acetyl esterase (RGAE). 

Only PAE, a novel acetyl esterase, could remove acetyl from beet pectin, to a maximum of 30%. This was shown to be one specific acetyl group in theJiomogalacturonan chain of pectin (smooth region) by NMR spectroscopy. PAE activity was influenced by buffer salts and the addition of bivalent cations. PAE worked cooperatively with pectolytic enzymes. 

Enzymes can be used to specifically modify the pectins. Pectin methyl esterase is already widely used to adjust the gelling properties of commercially available pectins. The acetyl esters also strongly affect the gelation [2,3] and removal is important for the upgrading of sugar beet pectin, extractable from a by-product of the sugar industry. 

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