Metabolic pathways context

Histidine phosphatases and aspartate phosphatases are well established in lower organisms, mainly in bacteria and in context with two-component-systems . Reversible phosphorylation of histidine residues in vertebrates is in its infancy. The first protein histidine phosphatase (PHP) from mammalian origin was identified just recently. The soluble 14 kD protein does not resemble any of the other phosphatases. ATP-citrate lyase and the (3-subunit of heterotrimeric GTP-binding proteins are substrates of PHP thus touching both, metabolic pathways and signal transduction [4]. 

Metabolic pathways containing dioxygenases in wild-type strains are usually related to detoxification processes upon conversion of aromatic xenobiotics to phenols and catechols, which are more readily excreted. Within such pathways, the intermediate chiral cis-diol is rearomatized by a dihydrodiol-dehydrogenase. While this mild route to catechols is also exploited synthetically [221], the chirality is lost. In the context of asymmetric synthesis, such further biotransformations have to be prevented, which was initially realized by using mutant strains deficient in enzymes responsible for the rearomatization. Today, several dioxygenases with complementary substrate profiles are available, as outlined in Table 9.6. Considering the delicate architecture of these enzyme complexes, recombinant whole-cell-mediated biotransformations are the only option for such conversions. E. coli is preferably used as host and fermentation protocols have been optimized [222,223]. 

Because of the polyfactorial nature of disease states, such as obesity, type 2 diabetes, and Metabolic Syndrome, it is expected that drugs targeting the lipid synthesis and metabolism pathways will be used in the context of combination therapy [7]. Pre-clinical and clinical results to date indicate that pronounced efficacy could be achieved toward the management of associated lipid levels and insulin resistance, and thus, investigation in these areas provides significant promise. 

Empath provides a view of a reaction in the context of metabolic pathways. As such, it serves as an index for other Cabinet databases. 

A principle in metabolic regulation that allows one to identify the inhibited step within a metabolic pathway as that reaction for which the concentrations of reactants and products rise and fall, respectively, from their steady-state values when an inhibitor is introduced. In the context of the electron transfer chain, the crossover-point refers to that reaction step demarking the transition from more reduced to more oxidized respiratory enzymes. 

For these reasons, microbial sensors are less suitable for the determination of individual analytes. However, some practical apphcations for biosensors based on enzymes or antibodies for the specific determination of environmentally relevant compounds can be expected soon [11]. Furthermore, in some cases defined specific metabolic pathways in microorganisms are used, leading to microbial sensors for more selective analysis for those environmental pollutants which cannot be measured by the use of simple enzyme reactions, e.g., aromatic compounds and heavy metals. In this context it is also important to mention the aspect of bio availability, a parameter which is included by the measuring procedure of microbial sensors as an integral effect. 

In this chapter, step and intermediate refer to chemical species in the reaction pathway of a single enzyme-catalyzed reaction. In the context of metabolic pathways involving many enzymes (discussed in Part II), these terms are used somewhat differently. An entire enzymatic reaction is often referred to as a step in a pathway, and the product of one enzymatic reaction (which is the substrate for the next enzyme in the pathway) is referred to as an intermediate. ... 

To appreciate fully the significance of individual metabolic pathways and their regulation, we must view these pathways in the context of the whole organism. An essential characteristic of multicellular organisms is cell differentiation and division of labor. The specialized... 

Specific vanadium-induced alterations in the activity or expression level of components of metabolic pathways are described here. Many of these changes are not caused by alterations in the pathway enzymes themselves but in enzymes and factors involved in regulation, commonly referred to as signal transduction systems. Section 11.3 will discuss the alterations described in this section in the context of general signal transduction processes affected by vanadium. 

The major oxidative drug-metabolizing pathway is catalyzed by cytochrome P450 enzymes (Mulder, 2006). The abbreviation CYP is typically used in this context. More than 60 CYPs have been identified. These are identified by up to four characters (letters or numbers). For example, in the term CYP2A4 4 the letters and numbers indicate the following ... 

It is doubtful that the data available justify quite such a sweeping statement. First, although the physiological functions of many compounds they mention are indeed unknown, it may not be fair to take them out of the context of metabolic pathways. They may be intermediates in the synthesis of pigments, hormones, or other compounds of known function. Conflicting reports on their rate of turnover exist. Second, the reviewers did not correlate plant chemistry specifically with feeding preference they simply assumed that taxonomically (basically that means morphologically) related plants would be similar in their chemical composition. In a very simple, direct way, the work of Brower (below) indicates that this assumption cannot be made. Third, we still need more cause-and-effect evidence for the relationship between plant... 

Conceptual Insights, Overview of Carbohydrate and Fatty Acid Metabolism. View this media module to gain a "bigger picture" understanding of the roles of the pentose phosphate pathway in the context of other metabolic pathways (glycolysis, citric acid cycle, glycogen and fatty acid metabolism). 

It is clear that more molecular chronometers need to be analysed. On account of the universality of the core metabolic pathways, a molecular study of the enzymes of central metabolism may prove worthwhile in this context. Moreover, the range of phenotypes within the one domain (e.g. extreme halophilicity and thermophilicity, in addition to mesophilicity) may make a comparative study of these enzymes especially valuable to our understanding of the structural basis for extreme protein stability. For these reasons, a number of laboratories are currently engaged in detailed structure-function investigations of the central metabolic enzymes. For a detailed discussion of the comparative enzymology of these pathways, see ref [1]. 

We focus on the combination of transcriptomics and metabolomics and more specifically on microarray data, which is currently the most used method for gene expression profiling and is used on a routine basis. In the first paragraphs, we briefly revise the extraction of mRNA or metabolites, their measurement, quality control of data, and analysis methods. Afterward two different types of data fusion and recent tools and publications are reviewed, followed by visualization methods for obtained data. Lastly, the metabolite annotation Web server MassTRIX is presented. This Web server allows combined analysis of transcriptomic and metabolomic data in the context of metabolic pathways. We compared the metabolomics part against similar tools and give a short outlook on the next version of MassTRIX, MassTRIX 4. 

Another local anesthetic used in mesotherapy, Kdocaine, goes through a different metabolic pathway from procaine, being converted into monoethylglycine, xylididide (MEGX) and acetaldehyde. Its action in this context must therefore have a different basis from that of procaine. 

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