Enzyme sensitivity

Enzymology of proteases in a water-phase is well known, but its alteration in a compartment is poorly understood. There are dramatical changes in reaction rates, in enzyme contractions and in enzyme sensitivity to inhibitors, which are not exactly described. In addition, besides fibrin and platelets there are several cellular and molecular components present in a thrombus compartment, where their influence on the basic fibrinolytic reactions is not known. To study this aspect of fibrinolysis is a task of the near future [4]. 

Since biosynthesis of IMP consumes glycine, glutamine, tetrahydrofolate derivatives, aspartate, and ATP, it is advantageous to regulate purine biosynthesis. The major determinant of the rate of de novo purine nucleotide biosynthesis is the concentration of PRPP, whose pool size depends on its rates of synthesis, utilization, and degradation. The rate of PRPP synthesis depends on the availabihty of ribose 5-phosphate and on the activity of PRPP synthase, an enzyme sensitive to feedback inhibition by AMP, ADP, GMP, and GDP. 

Enzymes Enzyme- sensitive component Component forming molecular self-assembly Mode of formation References... 

Enzyme-sensitive supramolecular polymers also hold promise in analytical applications such as the screening of enzyme inhibitors. A simple visual assay based on the hydrogelation of small molecules has been developed for screening the activities of inhibitors of enzymes like acid phosphatase. A number of inhibitors for... 

As noted earlier, protein structure is stabilised by a series of weak forces which often give rise to the properties which are functionally important (models of active sites and substrate binding are discussed above). On the other hand, because active sites involve a set of subtle molecular interactions involving weak forces, they are vulnerable and can be transformed into less active configurations by small perturbations in environmental conditions. It is therefore not surprising that a multitude of physical and chemical parameters may cause perturbations in native protein-geometry and structure. Thus, enzyme deactivation rates are usually multi-factorial, e.g. enzyme sensitivity to temperature varies with pH and/or ionic strength of the medium. 

The repair process can be measured by several techniques of varied complexity. These include measurement of adduct formation and the rate of its disappearance, the detection of enzyme-sensitive sites, and the measurement of strand breaks. Replacement of the damaged region, which is the... 

Each preparation is separated into four phases (I) The tissue treatment phase includes how to handle tissue so there is no cross-contamination of samples and how to grind, powder, or macerate the tissue to enhance isolation. (II) The lysis phase includes how to differentially lyse the cellular membrane and the mitochondrial membrane and how to isolate mitochondria away from the rest of the cell. (Ill) The purification phase includes techniques for extracting purified and enzyme-sensitive DNA from the lysis phase. (IV) The assay phase shows how to assay the final product of the preparation by agarose gel electrophoresis and offers some suggestions as to how to assess the purity of the isolated DNA. 

The action of the most prevalent enzyme can be neutralised [123] (see also p. 362), thus allowing an enzyme-sensitive /3-lactam antibiotic to inhibit growth. The concentrations of antibiotic necessary to achieve this effect were high and the authors felt that the concept could be achieved only in urine infections. This has met with some success in the clinical situation [115] but such combinations are not widely used. Combinations of carbenicillin with methicillin showed only minimal enhancement in vitro against Ps. aeruginosa [103]. 

Figure 5.4 Changes in certain allosteric enzyme sensitivities of A. n er in citric acid produdng mode compared to general metabolism. Conditions required for citric add accumulation manganese deficiency ferrous ion deficiency low pH high concentration of glucose.

Enzyme 0.228 mM in 0.1 M phosphate buffer (pH 7.0), temperature 105 K, 100 kHz modulation frequency, 1.0 mT modulation amplitude, 2 mW power (20 dB), 0.2 s time constant, 0.10 mTls scan rate, 9.39148 GHz microwave frequency. Key 1, oxidized enzyme P as 1, but 5 X instrument sensitivity 2, reduced enzyme, sensitivity as in V 3, oxidized enzyme, lyophilized at 0 C, redissolved. Asm Agio = 1.1 4, oxidized enzyme, after treatment with Chelex 100, AisolAno = 1.0, sensitivity in 3 and 4 as in V. (Reproduced, with permission, from Ref. 18. Copyright 1979,... 

Antigen Electrode Principle Marker enzyme Sensitivity References... 

The importance of preserving enzymes has been discussed earlier in this chapter. The activity of enzymes is usually measured by performing an assay specific to the enzyme being tested. It is also recommended to conduct washing tests over an extended time period on enzyme-sensitive stained fabrics and determine the extent of enzyme loss as a function of time. 

In eukaryotes RNA is synthesized by three different RNA polymerases, each of which mediates the synthesis of a distinct product. RNA polymerase I (or A) synthesizes 25S and 18S rRNA. RNA polymerase II (or B) produces mRNA, whereas RNA polymerase III (or C produces t(ransfer)RNA and 5S rRNA. Each enzyme has its own characteristics that can be used to follow the purification of the individual enzymes. Sensitivity to a-amanitin is a useful property to characterize the polymerases. RNA polymerase II is highly sensitive to this toxin, whereas polymerase I is insensitive. Polymerase III varies in sensitivity from species to species but is in general less sensitive than polymerase II. 

It may now be possible to hypothesize why acetaminophen, like aspirin, is antipyretic, but it exhibits minimal antiinflammatory properties at therapeutic doses. Acetaminophen has been shown to inhibit PG synthetase in brain areas well, but much less so in peripheral areas. This is most likely due to differences in the enzyme sensitivities to these drugs in different parts of the body (isozyme ). 

In addition, the degradation properties of hydrogels were adjusted by incorporation of degradable linkers. By using enzyme-sensitive peptide sequences, cell-responsive biomaterials that mimic the proteolytic recognition of natural ECMs... 

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