Hydrolytic activity

Total activity Alcoholytic activity Hydrolytic activity... 

There is evidence for the presence of active hydrolytic and proteolytic enzymes within the nasal mucosal, including various aminopeptidases (25). Hussain et al (31) have reported extensive enzymatic hydrolysis of leucine enkephalin, intranasally, which can be inhibited in vitro by various competitive di-and tripeptide fragments. The data on nasal peptidase activity is too incomplete to predict the metabolic consequences for other peptide drugs. 

For determining the absolute concentration of active hydrolytic enzymes, active site titrants, a sort of quasi-substrates, have been developed. The catalytic pathway... 

The phosphotriesterase-catalyzed reaction involves an SN2-type mechanism, with inversion of configuration at the phosphorus atom [708] activated water is presumed to attack the electrophilic phosphorus of the substrate, shown as an attack on diethyl 4-nitrophenyl phosphate (a non-biological substrate) in Figure 26(b). Both zinc ions work to activate hydrolytic water and polarize the P-0 bond [77i, 114]. 

Thermal stability of soluble or immobilized enzyme was determined by incubating the biocatalyst in 100 mM sodium phosphate buffer pH 7.0 at 50 or 60 °C. Periodically, samples were withdrawn, and their residual activities were assayed by the hydrolysis of methyl butyrate. Residual activity is given as percentage of initial activity (hydrolytic activity before incubation). Thermal deactivation curves have been described following the... 

Figure 3.2 Schematic of cellular uptake ofnonviral vector DMA complexes and evasion from lysosomal degradation (a) shows the general proposed method and (b) Illustrates more detailed mechanism of endolysosomal escape. In (b), the top figure outlines normal lysosomal degradation through active hydrolytic enzymes due to the buffering capacity of many polycations, hydrolytic enzymes are not activated and the DNA-polymer complex is able to escape degradation (lower figure).

Since trypsin is a mixture, it has no well-defined optimum pH. It should also be noted that trypsin is the only hydrolytic enzyme which is at all active in alkaline solution. 

Perhaps the most extensively studied catalytic reaction in acpreous solutions is the metal-ion catalysed hydrolysis of carboxylate esters, phosphate esters , phosphate diesters, amides and nittiles". Inspired by hydrolytic metalloenzymes, a multitude of different metal-ion complexes have been prepared and analysed with respect to their hydrolytic activity. Unfortunately, the exact mechanism by which these complexes operate is not completely clarified. The most important role of the catalyst is coordination of a hydroxide ion that is acting as a nucleophile. The extent of activation of tire substrate througji coordination to the Lewis-acidic metal centre is still unclear and probably varies from one substrate to another. For monodentate substrates this interaction is not very efficient. Only a few quantitative studies have been published. Chan et al. reported an equilibrium constant for coordination of the amide carbonyl group of... 

Inspired by the many hydrolytically-active metallo enzymes encountered in nature, extensive studies have been performed on so-called metallo micelles. These investigations usually focus on mixed micelles of a common surfactant together with a special chelating surfactant that exhibits a high affinity for transition-metal ions. These aggregates can have remarkable catalytic effects on the hydrolysis of activated carboxylic acid esters, phosphate esters and amides. In these reactions the exact role of the metal ion is not clear and may vary from one system to another. However, there are strong indications that the major function of the metal ion is the coordination of hydroxide anion in the Stem region of the micelle where it is in the proximity of the micelle-bound substrate. The first report of catalysis of a hydrolysis reaction by me tall omi cell es stems from 1978. In the years that... 

Mocimycin has been chemically converted to aurodox by protection of the 4-hydroxy group at the pyridone moiety as the benzoylformate, followed by /V-methylation and hydrolytic removal of the protective group (1,55). Whereas aurodox esters are active growth promotors in animals, goldinamines that are A/-acylated by acids other than goldinonic acid, such as acetic, benzoic, or arylsulfonic acids, lack useful antimicrobial or growth-promoting activity (1). 

The antibacterial effectiveness of penicillins cephalospotins and other P-lactam antibiotics depends upon selective acylation and consequentiy, iaactivation, of transpeptidases involved ia bacterial ceU wall synthesis. This acylating ability is a result of the reactivity of the P-lactam ring (1). Bacteria that are resistant to P-lactam antibiotics often produce enzymes called P-lactamases that inactivate the antibiotics by cataly2ing the hydrolytic opening of the P-lactam ring to give products (2) devoid of antibacterial activity. 

Pha.rma.ceutica.ls. Neopentanoic acid derivatives are widely used in the preparation of pharmaceuticals, eg, as a means of introducing the tert-huty group into a molecule. More frequendy, however, derivatives have been prepared that exploit the enhanced hydrolytic stabiUty of the neopentanoate group. Eor example, when salmon calcitonin is treated with N-hydroxysuccinimide pivalate [42014-50-6], the resulting derivative retains the biological activity of the precursor, but gives an extended duration of activity (51). 

Lipases are also active during a certain period of the drying step (51), eg, Lipolase displays maximum activity when the moisture content on the fabric is 20—30% by weight. This means that significant decomposition of any residual fatty matter will take place while the laundry is drying. This hydrolytic activity does not result in an immediate advantage in terms of fat removal however, next time the stained fabric is washed the stain will be removed more effectively. 

The transformations described thus far were catalyzed by enzymes in their traditional hydrolytic mode. More recent developments in the area of enzymatic catalysis in nonaqueous media (11,16,33—35) have significantly broadened the repertoire of hydrolytic enzymes. The acyl—enzyme intermediate formed in the first step of the reaction via acylation of the enzyme s active site nucleophile can be deacylated in the absence of water by a number of... 

By virtue of their fused /3-lactam-thiazolidine ring structure, the penicillins behave as acylating agents of a reactivity comparable to carboxylic acid anhydrides (see Section 5.11.2.1). This reactivity is responsible for many of the properties of the penicillins, e.g. difficult isolation due to hydrolytic instability (B-49MI51102), antibacterial activity due to irreversible transpeptidase inhibition (Section 5.11.5.1), and antigen formation via reaction with protein molecules. 

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