Destruction enzymatic

Chemical lysis, or solubilization of the cell wall, is typically carried out using detergents such as Triton X-100, or the chaotropes urea, and guanidine hydrochloride. This approach does have the disadvantage that it can lead to some denaturation or degradation of the produci. While favored for laboratory cell disruption, these methods are not typically used at the larger scales. Enzymatic destruction of the cell walls is also possible, and as more economical routes to the development of appropriate enzymes are developed, this approach could find industrial application. Again, the removal of these additives is an issue. 

Active reuptake of the neurotransmitter into the synaptic knob of the presynaptic neuron for reuse or enzymatic destruction... 

Diffusion from the synapse into the circulation and ultimate enzymatic destruction in the Uver and renal excretion. 

Some of the indirectly acting adrenomimetic amines are used primarily for their vasoconstrictive properties. They are applied locally to the nasal mucosa or to the eye. Other amines are used as bronchodilators, while still others are used exclusively for their ability to stimulate the CNS. Many noncatecholamine adrenomimetic amines resist enzymatic destruction, have prolonged actions, and are orally effective. The indirectly acting drugs are effective only when given in large doses, and they often produce tachyphylaxis. 

At their 3 end, most eukaryotic mRNAs have a string of 80 to 250 A residues, making up the poly(A) tail. This tail serves as a binding site for one or more specific proteins. The poly(A) tail and its associated proteins probably help protect mRNA from enzymatic destruction. Many prokaryotic mRNAs also acquire poly(A) tails, but these tails stimulate decay of mRNA rather than protecting it from degradation. 

Development of synthetic antiviral compounds is hardly beyond its infancy/ Serious problems must be overcome with most of these compounds. Toxicity (sometimes carcinogenicity), development of resistance by viruses, and enzymatic destruction limit the utility of most drugs. For example, adenosine deaminase destroys Ara-A quite rapidly. With our rapidly advancing knowledge of viral life... 

Both the cephalosporins and the penicillins owe their antibacterial action to their ability to block bacterial cell-wall biosynthesis. Cephalosporin C is less active than the penicillins, but is less susceptible to enzymatic destruction by /3-lactamases, which are enzymes that cleave the lactam ring. In fact, the so-called resistance of staph bacteria to penicillins is attributed to the propagation of strains that produce /3-lactamase. Numerous semisynthetic penicillins and cephalosporins have been made in the hope of finding new broad-spectrum antibiotics with high activity but with greater /3-lactam stability. Several of these are in clinical use. 

By virtue of their size and charge, peptide molecules are not the ideal candidates for transfer into the systemic circulation following instillation in the nose. Among the many barriers to absorption that must be overcome are mucociliary clearance, extracellular enzymatic destruction, the lipophilic bilayer membrane of nasal epithelial cells, the potential for nasal epithelial cells to degrade any peptide molecules that cross the lipid bilayer, and the potential to establish futile cycles of endocytosis and exocytosis on the apical surface of polarized epithelial cells. Indeed, in the face of these multiple barriers, it seems all the more remarkable that any substantial absorption of peptide drugs from the nose has ever been observed. Despite these barriers, recent... 

Monoamine Oxidase Inhibitors. Monoamine oxidase (MAO) is an enzyme that is located at amine synapses and helps remove released transmitters through enzymatic destruction. Drugs that inhibit this enzyme allow more of the transmitter to remain in the synaptic cleft and continue to exert an effect.74 As with... 

Finally, ACE inhibitors exert some of their beneficial effects by increasing bradykinin levels in the bloodstream.17,70 Bradykinin is a vasodilator, and increased levels of this compound decrease cardiac workload in people with heart failure. Normally, ACE is responsible for the enzymatic destruction of bradykinin in the bloodstream. ACE inhibitors reduce the breakdown of bradykinin, thereby prolonging the vasodilating effects of this substance.17,70... 

The actions of acetylcholine released from autonomic and somatic motor nerves are terminated by enzymatic destruction of the molecule. Hydrolysis is accomplished by the action of acetylcholinesterase, which is present in high concentrations in cholinergic synapses. The indirect-acting cholinomimetics have their primary effect at the active site of this enzyme, although some also have direct actions at nicotinic receptors. The chief differences between members of the group are chemical and pharmacokinetic—their pharmacodynamic properties are almost identical. 

One is that the mouse is inherently resistant to many mutagens. When a highly reactive chemical, one that binds tightly to serum or tissue components immediately on administration, or one that is subject to rapid enzymatic destruction is administered, it is possible that only an... 

Synaptic Clearance Antagonists. By preventing the removal of naturally-released transmitter from the region of its receptors, the effect of the neuromesssenger on the receiving cell will be prolonged and intensified. There are three principal routes by which neuromessengers are removed from the synaptic cleft (i) enzymatic destruction of the transmitter (e.g., acetylcholine (ACh) which is hydrolyzed in the synaptic cleft by acetylcholinesterase) (ii) uptake into pre- and post- synaptic cells by membrane-associated pumps that have substantial specificty for molecules they will carry (iii) diffusion away from the cleft. 

Work by Sabath and Abraham [186] indicated that the inducible enzyme played some role in the resistance of Ps. aeruginosa to penicillins and cephalosporins. Experiments with benzylpenicillin showed that the organism grew only when the concentration of antibiotic in the medium had been reduced by enzymatic destruction. Figure 7.6 shows the growth of Ps. aeruginosa in the presence of relatively low concentrations of benzylpenicillin. Growth occurs only when the antibiotic concentration has been reduced to a value well below the MIC. 

The effector response is rapidly terminated through enzymatic destruction by acctylcholinestcrase. 

In the preparation of semisynthetic cephalosporins, the following improvements are sought (a) increased acid stability, (b) improved pharmacokinetic properties, particularly better oral ab.sorption, ic) broadened antimicrobial spectrum. (d) increased activity agaiast resistant microorganisms (as a result of resistance to enzymatic destruction, improved penetration. increased receptor affinity, etc.), (e) decreased allergenicity, and (f) increased tolerance after parenteral administration. 

The mechanisms of resistance can vary. In bacterial resistance to antibiotics, these include pumping the antibiotic out of the cell, changing the cell wall to avoid the antibiotic, enzymatic destruction of the antibiotic, and the development of substitute proteins not targeted by the antibiotic.24 It may take longer to develop resistance in insects and plants than in microorganisms simply because the generation times are longer. 

Acetic acid does not cause the alpha to beta shift of aspartic acid, while even a dilute solution of strong mineral acids such as hydrochloric or sulfuric acid brings it about. Even though the beta-aspartyl analog in terms of pressor activity equals that of angiotensin itself, it is not split by the plasma enzyme angiotensinase A. Use of angiotensin with the beta-aspartyl impurity present could lead to erroneous conclusions, especially in studies on rates of enzymatic destruction. 

Viruses are one of the smallest biological entities (except viroids and prions) that carry all the information necessary for their own reproduction. They are unique, differing from procaryotes and eucaryotes in that they carry only one type of nucleic acid as genetic material, which can be transported by the vims from one cell to another. Viruses are composed of a shell of protein enclosing a core of nucleic acid, either ribonucleic acid (RNA) or deoxyribonucleic acid (DNA), that codes for viral reproduction. The outer shell serves as a protective coat to keep the nucleic acid intact and safe from enzymatic destruction. In addition to their protein coat, some viruses contain an outer covering known as an outer envelope. This outer envelope consists of a lipid or polysaccharide material. 

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