Esterase, enzymatic activity

TOCP produces a delayed neurotoxicity, by inhibiting a nonspecific neuronal carboxylesterase, neuropathic target esterase. The neuropathic target esterase appears to have a role in neuronal lipid metabolism. Neuropathic target esterase enzymatic activity is highest in nervous tissue. 

The strains were cultured on Mandels medium + 1% citrus pectin for 5 days and the enzymatic activities of culture filtrates were determined on three substrates citrus pectin, polygalacturonic acid and filter paper, (a) extracellular proteins are in p.g/ml. (b) p>ectinolytic activities on pectin (PC) and on polygalacturonic acid (TO) and Pectin esterase (PE) are in units/ml. (c) total cellulolytic activity (filter paper, fp) are in mg of liberated reducing sugars/ml. 

In conclusion, sydnonimines represent a class of NO-donors that, with the exception of N-acylated derivatives that need chemical hydrolysis or enzymatic activation by esterases, release NO spontaneously in the presence of oxidants without requiring further activation with enzymes or thiols. 

Many receptors have been identified in all cases they are proteins. Some of the proteins have enzymatic activity. Eor instance, dihydrofolate reductase is a receptor for antifolates and acetylcholine esterase is a receptor for organophosphates. Some receptors serve as transport vehicles across the cellular membranes, as is the case with the receptors for steroid hormones (Baxter and Eorsham, 1972). Specific receptors may be confined to certain tissues or may be distributed among all the cells of an organism. 

Many enzymes are named by adding the suffix -ase to a word, or words, descriptive of the type of enzymatic activity. Thus, esterases hydrolyze esters, proteinoses hydrolyze proteins, reductases achieve reductions, and synthetases achieve syntheses of polypeptide chains, nucleic acid chains, and other molecules. 

Instruments of this type may also be used quite effectively to evaluate kinetics of time-dependent changes in foods, be they enzymatic or reactive changes of other types. The computerized data-acquisition capabilities of these instruments allow precise measurement of absorbance or fluorescence changes, often over very brief time periods ( milliseconds). This is particularly useful for analysis of fluorescence decay rates, and in measurement of enzymatic activity in situ. A number of enzyme substrates is available commercially which, although non-fluorescent initially, release fluorescent reaction products after hydrolysis by appropriate enzymes. This kinetic approach is a relatively underused capability of computerized microspectrophotometers, but one which has considerable capability for comparing activities in individual cells or cellular components. Fluorescein diacetate, for example, is a non-fluorescent compound which releases intensely fluorescent fluorescein on hydrolysis. This product is readily quantified in individual cells which have high levels of esterase [50]. Changes in surface or internal color of foods may also be evaluated over time by these methods. 

The oral mucosa, in common with other mucosa, shows enzymatic activity, in particular esterase and peptidase activity. Depending on the animal species and substrates used, buccal homogenates have shown enzyme activites between a few and several hundred percent of the activities of intestinal homogenates. 

Separation analysis at the outlet of the detector must respect three major conditions. The first is the cell integrity (i.e., the diagnosis of the particle). This can be operated on line, by means of classical photometric devices operated in the light-scattering mode (opacimetry) at 254 nm. Off-line methods, after fraction collection, are possible and recommended, by microscopy and granulometric analysis (Coulter counting). The second objective is to analyze cell viability. Off-line methods after fraction collection are equally possible. The blue trypan exclusion test, motility measurements, or specific enzymatic activities (esterase) can be performed on an aliquot of the collected fraction. 

Metabolism also plays a critical role in the pharmacology of cocaine. The rapid hydrolysis of cocaine via two different pathways leads to its rapid inactivation/detoxification. This rapid metabolism has been a major determinant in the methods and modes of cocaine abuse. Identification and characterization of these hydrolytic enzymes would be useful in that selective induction of these enzymes offers a potential treatment strategy for dealing with cocaine overdose. It is conceivable that long-term elevation of the enzyme or enzymatic activity could be used in conjunction with maintenance therapy for cocaine addicts. Hydrolases or esterases are also responsible for the transesterfication of cocaine. The pharmacological effect of cocaine is prolonged and enhanced when cocaine is used in conjunction with ethanol. A carboxylesterase catalyzes an ethyl transeterification of cocaine to cocaethylene, which is biologically active. 

Continuous assays are rarely described for lipases, but are frequently described for esterases. Similar to lipases, esterases hydrolyze ester bonds. However, in contrast to lipases, their substrates are water-soluble and thus water-soluble fluorescent substrates can be used to measure their enzymatic activity. Some of these water-soluble substrates have been proposed for the measurement of lipolytic ac-... 

Factor VII is the only coagulation foctor in the circulating blood which has enzymatic activity in its native form (03). While Factor VII has esterase activity, it must interact with tissue thromboplastin to form a potent activator of Factor IX or Factor X (05). An assay which could detect the presence of Factor Vila in the circulation could help to screen for those patients at a high risk for cardiovascular disease. 

The principle of assaying inhibitors by synthetic substrate methodology is simple. In the presence of an excess of the enzyme under study, the enzymatic activity remaining after reaction with the inhibitor is inversely related to the concentration of the inhibitor. Because reliable and easy to perform techniques with natural substrates have not been available, synthetic substrate assays for inhibitors have gained wide acceptance and commercial kits for some are available. Some of the inhibitors which are of interest are antithrombin III, a -antiplasmin, a -antitrypsin. Cl esterase inhibitor, and... 

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