Enzymes decreasing

Streptokinase has an initial plasma half-life (/ 2 of 18 min, and a P half-life of 83 min (73) it is well recognized that the thrombolytic efficacy of the enzyme decreases as the age of the thrombus increases thus, thrombolysis is significantly decreased when therapy is initiated more than three hours after an occlusion (74). 

Enzymes decrease the activation energy of chemical reactions... 

Calcium carbonate or magnesium hydroxide antacids may decrease the effectiveness of the digestive enzymes. When administered concurrently with an iron preparation, the digestive enzymes decrease the absorption of oral iron preparations. 

A decreased glycolytic rate has been proposed as a cause of muscle fatigue and related to pH inhibition of glycolytic enzymes. Decreasing pH inhibits both phosphorylase kinase and phosphofructokinase (PFK) activities. PFK is rate determining for glycolytic flux and therefore must be precisely matched to the rate of ATP expenditure. The essential characteristic of PFK control is allosteric inhibition by ATP. This inhibition is increased by H and PCr (Storey and Hochachka, 1974 ... 

St. John s wort Increase metabolism of COCs via induction of various cytochrome P-450 enzymes Decrease efficacy of COCs avoid use with COCs... 

It was postulated that the differences in enzyme activity observed primarily result from interactions between enzyme-bound water and solvent, rather than enzyme and solvent. As enzyme-associated water is noncovalently attached, with some molecules more tightly bound than others, enzyme hydration is a dynamic process for which there will be competition between enzyme and solvent. Solvents of greater hydrophihcity will strip more water from the enzyme, decreasing enzyme mobility and ultimately resulting in reversible enzyme deactivation. Each enzyme, having a unique sequence (and in some cases covalently or noncovalently attached cofactors and/or carbohydrates), will also have different affinities for water, so that in the case of PPL the enzyme is sufficiently hydrophilic to retain water in all but the most hydrophilic solvents. 

TPMT2 G238C Alanine to proUne 0.2-0.5 Low to intermediate because of enhanced degradation of enzyme Decreased methyla-tion of AZA to inactive compounds Hematologic and GI toxicity... 

The enzymes in this pathway are (1) renin, (2) angiotensinconverting enzyme (ACE) and (3) aminopeptidase. The key enzyme in this pathway is ACE. Drags that inhibit this enzyme decrease the formation and hence the concentration of angiotensin-II, which lowers blood pressure. Compounds that inhibit this enzyme are very successful antihypertensive drags (discussed in detail in Chapter 22). 

Consider an enzyme at the beginning of a pathway whose pathway-substrate concentration is much less than that required to saturate the enzyme (see Figure 3.7), e.g. similar to or lower than that of the K. As the catalysis proceeds, the concentration of substrate falls so that the activity of the enzyme decreases more and more. Consequently, the activity of such an enzyme cannot maintain a constant flux through a pathway, so that a steady state cannot be achieved. 

Hepatic Effects. The liver is a common target organ for substituted furan compounds (Boyd 1981). Ten days of oral exposure of female mice to a dose of 591 mg/kg/day of 2,3-benzofuran altered the activity of several hepatic enzymes, decreasing the rate of reactions which activate electrophiles and increasing the rate of reactions which deactivate electrophiles (Cha et al. 1985 Heine et al. 1986). No toxicity was reported in this study (Cha et al. 1985 Heine et al. 1986). Liver damage was seen in rats exposed to... 

Low y and Wj values correspond to small spherical reversed micelles. In these structures the enzymes are forced into the interfacial film between the oil and the water. In contrast to lipases which are activated by interfaces, alcohol dehydrogenases show much lower activity under these circumstances. With increasing water concentration (increasing Wj) the reversed micelles grow. As a result, the influence of the interface on the enzyme decreases, enhancing the activity of an ADH, as shown in Fig. 4. 

Solvent polarity is known to affect catalytic activity, yet consistent correlations between activity and solvent dielectric (e) have not been observed [12,102]. However, a striking correlation was found between the catalytic efficiency of salt-activated subtilisin Carlsberg and the mobility of water molecules (as determined using NMR relaxation techniques) associated with the enzyme in solvents of varying polarities (Figure 3.11) [103]. As the solvent polarity increased, the water mobility of the enzyme increased, yet the catalytic activity of the enzyme decreased. This is consistent with previous EPR and molecular dynamics (MD) studies, which indicated that enzyme flexibility increases with increasing solvent dielectric [104]. 

Inhibitors of the microsomal enzymes decreased the covalent binding and the Clara cell necrosis and increased the LD50, even though the blood and pulmonary levels of ipomeanol... 

The maximum of the Gibbs free enthalpy between the ground states of substrate and product forms the Gibbs free enthalpy of activation with the energy difference AG7, which determines the rate constant of the reaction, like every catalyst, an enzyme decreases the value of AG and thus accelerates the reaction. (An agent increasing the value of AG7 is termed an anti-catalyst .)... 

There are three distinct findings for the effect of temperature on enzyme activity and stability in carbon dioxide. The first is that as temperature increases, activity of the enzyme decreases. Nakamura et al. (1986), Chi et al. (1988), and Lee et al. (1993) all observed slight decreases in activity as temperature was increased slightly. Chulalaksananukul et al. (1993) observed a more marked decrease in activity and attribute the loss of activity to thermal denaturation of the enzyme. 

Intestinal monoamine oxidase (MAO) metabolizes drugs such as sumatriptan,31 phenylephrine,32 and other amine-containing drugs. A number of hydrolytic and phase II enzymes, such as acetyl transferases, glutathione-S-transferases, methyl transferases, sulfo transferases, and UDP-glucuronosyl transferases, are also present in the intestinal mucosa (see Table 2.2). The amounts of metabolic enzymes decrease... 

They play an important role in maturation and differentiation of B and T lymphocytes, NK cells, macrophages, and cytokines they release Decrease amount of lymphocytes T helpers, have anti-inflammatory action, diminish allergenic responses of delayed type, depress mitogenic response of T cells, increase level of antioxidative enzymes, decrease number of free radicals... 

Lankinen YP, Inkeroinen MM, Pellinen J, Hatakka AI. The onset of ligninmodifying enzymes, decrease of AOX and color removal by white-rot fungi grown on bleach plant effluents. Water Sci Technol 1991 24(3-4) 189-198. 

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