Enzyme esterase

Although hydrolytic enzymes, esterases and amidases, are named after their major substrates, the same enzyme can often hydrolyze esters, thioesters, and amides therefore, the differentiation between esterases and amidases is sometimes artificial. The highest hydrolytic activity is in the liver, but the enzyme pseudocholinesterase is found in the serum. Gut bacteria also contain hydrolytic enzymes. 

The production of a quaternary ammonium salt from a tertiary amine and an alkyl halide forms the synthetic route to decamethonium, the first of a range of synthetic muscle relaxants having an action like the natural materials found in the arrow-poison curare. Decamethonium is actually a di-quaternary salt, as are more modem analogues, such as suxamethonium. Suxamethonium superseded decamethonium as a drug because it has a shorter and more desirable duration of action in the body. This arise because it can be metabolized by ester-hydrolysing enzymes (esterases) (see also Box 6.9). 

It is a cleavage of drug molecule by taking up a molecule of water. The most hydrolytic enzymes are found outside the endoplasmic reticulum, and in higher concentrations in liver, kidney and plasma. The metabolism of an ester by an enzyme esterase results in the formation of an acid and alcohol. The examples are meperidine, procaina-mide, pethidine and lidocaine etc. Meperidine is catalyzed by esterases to be changed into meperidinic acid and procainamide is catalyzed by amidases. 

Enzymes are proteinaceous catalysts peculiar to living matter. Hundreds have been obtained in purified and crystalline form. Their catalytic efficiency is extremely high—one mole of a pure enzyme may catalyze the transformation of as many as 10,000 to 1,000,000 moles of substrate per minute. While some enzymes are highly specific for only one substrate, others can attack many related substrates. Avery broad classification of enzymes would include hydrolytic enzymes (esterases, proteases), phosphorylases, oxidoreductive enzymes (dehydrogenases, oxidases, peroxidases), transferring enzymes, decarboxylases and others. 

The prodrug approach described above also can be used to alter the solubility characteristics, which, in turn, can increase the flexibility in formulating dosage forms. The solubility of methylprcdnisolonc can be altered from essentially water-insoluble methylpredni.solone acetate to slightly water-insoluble methylprednisolone to water-soluble meth-ylprednisolone. sodium succinate. The water-soluble sodium hemisuccinate salt is used in oral, intravenous, and intramuscular dosage forms. Methylprednisolone itself is normally found in tablels. The acetate ester is found in topical ointments and sterile aqueous suspensions for intramuscular injection. Both the succinate and acetate esters are hydrolyzed to the active methylprednisolone by the patient s own systemic hydrolytic enzymes (esterases). 

Acetylcholine is easily hydrolysed in the blood, both chemically and by enzymes (esterases and acetylcholinesterase). 

Phase 1 metabolizing enzymes include the CYP and FMO enzymes, esterases, and epoxide hydrolases, among others. These enzymes and the reactions they catalyze have been described in detail previously (Hodgson and Goldstein, 2001 Parkinson. 2001). The CYP and FMO families are perhap.s the best characterized because they are capable of catalyzing a wide range of reactions with broad substrate specificity. These enzymes are located in the endoplasmic reticulum of the cell and have been studied in many organs and tissues. 

Hitherto unreported (— )-conduramine E (170) was synthesized from 169 in ca. 50% overall yield as outlined in Scheme 27. Enzyme (esterase) induced monodeacetylation was followed by Mitsunobu-type inversion with an AT-nucleophile in the presence of acetic acid. endo-Cyclization with concomitant epoxide-opening produced a urethane bearing the correct stereochemistry at the four chiral centres. Base treatment revealed the (—)-conduramine [for (+)-conduramine E see Vol. 29, p. 

Biopolymers such as aliphatic polyesters are now produced on a semi-commercial scale by numerous companies that make biodegradable plastics [7]. Aliphatic polyesters have repeating units that are bonded via ester linkages and these natural esters can be degraded by enzymes (esterases) that are ubiquitous in nature... 

In their subsequent report, Raymond et al. used the encapsulated gold complex, Au-Ga4L5, in combination with enzymes, esterases, or lipases in a one-pot tandem reaction sequence. Enzymatic ester/imide hydrolysis of allenic ester or amide results in an intermediate [27], which subsequently undergoes... 

Keywords Biofunctionalization Cutinase Enzymes Esterase Lipase Poly(ethylene terephthalate) Polyester Thermostability... 

---