Enzymic activity metabolism

In addition to changes in metabolism that occur as a result of reduced hepatic enzyme activity, metabolism may be impaired by a reduction in hepatic mass, vol-... 

Figure 10.3-23. Metabolic model of glycolysis and tbe pentose phosphate pathway in E. coli. Squares Indicate enzyme activities circles indicate regulatory effects,...

Figure 1.20). All of these reactions, many of which are at apparent crosspurposes in the cell, must be fine-tuned and integrated so that metabolism and life proceed harmoniously. The need for metabolic regulation is obvious. This metabolic regulation is achieved through controls on enzyme activity so that the rates of cellular reactions are appropriate to cellular requirements. 

Regulation of enzyme activity is achieved in a variety of ways, ranging from controls over the amount of enzyme protein produced by the cell to more rapid, reversible interactions of the enzyme with metabolic inhibitors and activators. Chapter 15 is devoted to discussions of enzyme regulation. Because most enzymes are proteins, we can anticipate that the functional attributes of enzymes are due to the remarkable versatility found in protein structures. 

Metabolic regulation is achieved via regulating enzyme activity in three prominent ways allosteric regulation, covalent modi-... 

Evidence suggests that endosulfan can induce microsomal enzyme activity. Increased liver microsomal cytochrome P-450 activity was observed in male and female rats after single and multiple administrations of endosulfan (Siddiqui et al. 1987a Tyagi et al. 1984). Increased enzyme activity was observed in hepatic and extrahepatic tissues. Based on the increase in aminopyrine-A-demethylase and aniline hydroxylase activity, endosulfan has been shown to be a nonspecific inducer of drug metabolism (Agarwal et al. 1978). 

NEUTROPHILS HAVE AN ACTIVE METABOLISM CONTAIN SEVERAL UNIQUE ENZYMES PROTEINS... 

Various factors affect the activities of the enzymes metabolizing xenobiotics. The activities of these enzymes may differ substantially among species. Thus, for example, the possible toxicity or carcinogenicity of xenobiotics cannot be extrapolated freely from one species to another. There are significant differences in enzyme activities among individuals, many of which appear to be due to genetic factors. The activities of some of these enzymes vary according to age and sex. 

Table VI lists several drugs Inducing hepatic microsomal enzymes (5). These enzymes can metabolize the drug as well as other substrates. Barbiturates, grlseofulvln, and glutethlmlde Induce enzymes which metabolize coumarln and phenlndlone derivatives and thus reduce their anticoagulant activity. Dlphenylhydantoln and phenylbutazone stimulate cortisol hydroxylase activity and Increase the urinary excretion of B-hydroxy cortisol and decrease the concentration of cortisol In the plasma.

Figure 7.2 Biochemical pathways for the synthesis and metabolism of dopamine. (—) indicates drug inhibition of enzyme activity...

To date, there is very little known about if and how phytochemicals modulate the metabolism of GIT tissues other than the liver. Of particular interest are the xenobiotic metabolizing enzymes of the GIT, which are involved with transformation of drugs and toxins. Whereas the metabolic activities of the resident microflora dominate in the large intestine, mucosal enzyme activities are more important in the small intestine where bacterial densities are lower and the villi and microvilli increase the area of exposure. 

MCBAIN A J, MACFARLANE G T (2001) Modulation of genotoxic enzyme activities by non-digestible oligosaccharide metabolism in in-vitro human gut bacterial ecosystems. J Med Microbiol. 50 833-42. 

Livingstone DR, SV Farrar (1984) Tissue and subcellular distribution of enzyme activities of mixed-function oxygenase and benzo[a]pyrene metabolism in the common mussel Mytilis edulis L. Sci Tot Environ 39 209-235. 

Dangel W, R Brackmann, A Lack, M Mohamed, J Koch, J Oswald, B Seyfried, A Tschech, G Fnchs (1991) Differential expression of enzyme activities initiating anoxic metabolism of varions aromatic compounds via benzoyl-CoA. Arch Microbiol 155 256-262. 

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