Degradable enzymatically

Polysaccharides are hydrophilic natural polymers that can be degraded enzymatically. Block copolymers containing polysaccharide as a block were reviewed recently... 

The steady-state concentration of glycogen is regulated precisely by the coordination of separate synthetic and degradative enzymatic processes 538... 

The kinetics of disappearance from the circulation of intravenously administered human insulin (Fig. 6.32) is nonlinear [145]. Within a few minutes after injection, it becomes localized in the liver, heart, and kidneys, where it is rapidly metabolized. Indeed, the hepatic extraction could be as high as 70% on a single passage, whereas kidneys could account for 10-40% degradation. Enzymatic reduction of the disulfide bridges appears to be the first step in the in vivo metabolism of insulin, although this reaction appears of limited significance under in vitro conditions. 

The transport system of Bacillus subtilis accommodates the Fe " complexes of enterobactin (A-configured), enanfio-D-enterobactin and of corynebactin (bacilli-bactin) (both A). Since only A complexes can be bound to the receptor a configurational change from A to A is induced. Only the natural ferri-L-siderophores can be degraded enzymatically (399, 408). 

The natriuretic peptides have a short half-life in the circulation. They are metabolized in the kidneys, liver, and lungs by the neutral endopeptidase NEP 24.11. Inhibition of this endopeptidase results in increases in circulating levels of the natriuretic peptides, natriuresis, and diuresis. The peptides are also removed from the circulation by binding to ANPc receptors in the vascular endothelium. This receptor binds the natriuretic peptides with equal affinity. The receptor and bound peptide are internalized, the peptide is degraded enzymatically, and the receptor is returned to the cell surface. 

The discovery that D-gluconic acid 6-phosphate may be degraded enzymatically to D-ribose 5-phosphate17,18 has thrown light on a possible path for the biogenesis of D-ribose. 

Nidetzky, B., Steiner, W., and Claeyssens, M. 1995. Synergistic interaction of cellulases from Trichoderma reesei during cellulose degradation. Enzymatic Degradation of Insoluble Carbohydrates. ACS Symposium Series, 618, 90-112. 

Low molecular weight components in unfiactionated heparins have been identified long before the development of clinically effective agents. However, because of technologic problems, they were not made available for clinical use. The very first LMWH was obtained by a fractionation method (3). However, this method only yielded a limited amount of the active product and was cost prohibitive. During the past decade, different chemical and enzymatic processes have been developed to obtain LMWH from the parent unfiactionated heparin (UFH). The depolymerization process for the production of LMWH is shown in Figure 5. Such methods as chemical degradation, enzymatic depolymerization... 

Main components 1.5-2.5% sinalbin, a glucosinolate, which, after the addition of water, is degraded enzymatically by myrosinase into p-hydroxybenzyl isothiocyanate (not water-vapour volatile), glucose and sinapin hydrogensulphate. Sinapin constitutes the choline ester of sinapinic acid. Moreover, the plant contains app. 30% vegetable oil, mainly the glycerides of erucic acid, mucilage, steroids and proteins. 

There are different fashions how to induce water removal in condensation reactions. By simply heating amino acids with or without potent agents of condensations such as hydrogen cyanide, HC=N, cyan amide, N=C-NH2, and carbon-oxy-sulfide COS, oligomers and polymers, called proteinoids, readily formed. The detection of enzymatic activities in these polymeric proteinoids was unsuccessful except for about ten degrading enzymatic activities. Synthetic activities that build up molecules, for instance, kinase, ligase, and polymerase, were not detectable. The disadvantage of these mixtures of proteinoids is that they do not exhibit a distinct structure or a function. 

Water attacks the electron-deficient carbonyl atom targetting first a tetrahedral adduct, which then eliminates the amine fragment and produces the acid. The process is characterized by transferring the aminoacyl moiety of the peptide to water. In this type of group-transfer reaction the nucleophilic co-substrate is water 55.5 M water is the most nearly ubiquitous weak nucleophile in degradative enzymatic... 

TERMINATION OF THE ACTIONS OF CATECHOLAMINES The actions of NE and Epi are terminated by (1) reuptake into nerve terminals by NET (2) dilution by diffusion out of the junctional cleft and uptake at end organs and extraneuronal sites by ENT, OCTl, and OCT2. Subsequent to uptake, the catecholamines are subject to metabolic transformation by MAO and catechol-0-methyltransferase (COMT). In addition, catecholamines are metabolized by sulfotransferases (see Chapter 3). Termination of action by a powerful degradative enzymatic pathway, such as that provided by AChE in cholinergic transmission, is absent from the adrenergic system. Inhibitors of neuronal reuptake of catecholamines (e.g., cocaine, imipramine) potentiate the effects of the... 

Petersson et al. [1160] recently described a miniaturized flow-injection system for the determination of four different substrates, which each could be degraded enzymatically by means of appropriate oxidases according... 

From the fruits of Gleditsia japonica, which have been used in Japanese and Chinese folk medicine as a diuretic and expectorant, seven saponins (gleditsiasaponins B, C, Dj, D2, E, G and I) had been isolated. The structural elucidation of these saponins have been carried out by the chemical degradations, enzymatic hydrolysis and C-NMR spectra, and characterized as 3, 28-0-bisglycosides of echinocystic acid acylated with monoterpene carboxylic acid [46-49]. 

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