Characterization of Metabolism

In the overall metabolism of the living organism distinguished are exogenous metabolism, which comprises extracellular transformations of materials on the way to their uptake and excretion by the cells, and intermediary metabolism, which occurs in the cells. The intermediary metabolism is conceived as the sum total of chemical reactions that occur in the living cell. 

Functionally, metabolism encompasses the following major processes  

The sequences of chemical reactions involved form metabolic pathways, or cycles, each of these performing a definite function. 

Conventionally, central and special metabolic pathways are distinguished. Central pathways are common to the decomposition and synthesis of major macromolecules. Actually, they are much alike in all representatives of the living world. Special cycles are characteristic of the synthesis and decomposition of individual monomers, macromolecules, cofactors, etc. Special cycles are extremely diversified, especially in the plant kingdom. For this reason, the plant metabolism is conventionally classified into primary and secondary metabolisms. The primary metabolism includes the classical processes of synthesis and deeradation of major macromolecules (proteins, carbohydrates, lipids, nucleic acids, etc.), while the secondary metabolism ensuing from the primary one includes the conversions of special biomolecules (for example, alkaloids, terpenes, etc.) that perform regulatory or other functions, or simply are metabolic end byproducts. 

During catabolic and anabolic processes, a renovation of the molecular cellular components takes place. It should be emphasized that the catabolic and anabolic pathways are independent of each other. Be these pathways coincident and differing in the cycle direction only, the metabolism would have been side-tracked to the so-called useless, or futile, cycles. Such cycles arise in pathology, where a useless turnover of metabolites may occur. To avoid this undesirable contingency, the synthetic and degradative routes in the cell are most commonly separated in space. For example, the oxidation of fatty acids occurs in the mitochondria, while the synthesis thereof proceeds extramitochondrially, in the microsomes. 

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With the advent of modern LC/MS instrumentation and sophisticated software, metabolic profiling has gradually become a significant tool to support drug discovery. Early identification of active or toxic metabolites and characterization of metabolic liability of a particular structural series will significantly reduce the cycle time of the lead opti-... 

Because these different viability tests all reflect different aspects of cell viability, the choice of test depends on the aim of the study. For toxicity studies where biotransformation is an important bioactivation or detoxification step, metabolic function tests should be included to judge the validity of the method, whereas viability tests are needed to assess toxic effects. Both positive and negative controls should be included in such studies. When human liver is used, the characterization of metabolic activity is especially important because of the large inter-individual variability associated with this property [75]. 

Microcalorimetric characterization of metabolic trends in aquatic systems... 

Despite the high social relevance of infectious diseases and widespread use of animal cell lines in vaccine production, the application of even unstructured models for quantitative analysis and parameter estimation has not been common practice in bioprocess optimization. So far, research concerning influenza vaccine production in MDCK cell cultures has focused on the characterization of metabolism, growth of different cell lines and virus yields in various production systems [1,2]. 

Taken as a whole, the characterization of metabolic pathways in early drug... 

Hajduch, M., J.F. Casteel, K.E. Hurrehneyer, Z. Song, G.K. Agrawal, and J.J. Thelen. 2006. Proteomic analysis of seed filling in Brassica napus. Developmental characterization of metabolic isozymes using high-resolution two-dimensional gel electrophoresis. Plant Physiol. 141 32-46. 

G. (1978) A better cell line for making hybridomas secreting specific antibodies. Nature, 276, 269 -270. Niklas, )., Schrader, E., Sandig, V., Noll, T. et al. (2011) Quantitative characterization of metabolism and metabolic shifts during growth of the new human cell line AGEl.HN using time resolved metabolic flux analysis. Bioprocess. Biosyst. Eng, 34, 533-545. 

Human Metabolic Profiles. Characterization of Metabolic Processes by... 

Cren-Olive C, l,enoir M, Croq-l-emarrec F, Coddeville B, Salzet M, Rolando C. Characterization of metabolism site of flavan-3-ols by LC ESI MS/MS. 49th American Society for Mass Spectrometry Conference, Chicago, May 27-31, 2001. 

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