Metabolic Diversity

The signiflcance of toxic metabolites is important in diverse metabolic situations (a) when a pathway results in the synthesis of a toxic or inhibitory metabolite, and (b) when pathways for the metabolism of two (or more) analogous substrates supplied simultaneously are incompatible due to the production of a toxic metabolite by one of the substrates. A number of examples are provided to illustrate these possibilities that have achieved considerable attention in the context of the biodegradation of chlorinated aromatic compounds (further discussion is given in Chapter 9, Part 1) ... 

Drake HL, Daniel SL, Kiisel K, et al. 1997. Acetogenic bacteria what are the in situ consequences of their diverse metabolic versatilities Biofactors 6 13-24. 

Protein kinase B (Akt) is a serine/threonine, mitogen-regulated protein kinase involved in the protection of cells from apoptosis as well as the promotion of cell proliferation and diverse metabolic responses. It is activated upon binding of phospholipids and phosphorylation at residues Thr and Ser by upstream kinases such as phosphoinositide-dependent protein kinase 1 and 2 (M15). Activation of... 

The large and diverse metabolic capabilities of the liver enable it to metabolize many foreign compounds, but as metabolism does not always result in detoxication, this may make it a target (see sects. 7.2.1 and 7.2.4 chap. 7). 

Microorganisms, through their diverse metabolic abilities, are largely responsible for the chemical balance of the biosphere and for the degradation of a majority of the known 8-10 million organic compounds (Wackett, 1996). 

Liver cells comprise the cell nucleus (= karyoplasm) and the cell body (= cytoplasm). Hepatocytes and sinusoidal cells have various types of organelles in their eosinophilic cytoplasm such as endoplasmic reticulum, Golgi apparatus, lysosomes, mitochondria, peroxisomes, ribosomes, centrioles and kinetosomes. Numerous and diverse metabolic processes take place with their help. Almost all cytoplasmic structures of liver cells are continuously renewed (up to twice daily). (20, 27, 30, 33, 35, 46-48, 50, 53, 58, 59, 69, 74) (s. figs. 2.9, 2.16-2.18) (s. tab. 2.1)... 

The morphological and functional integrity of the liver is vital to the health of the human organism. This essentially depends upon constant maintenance of the numerous biochemical functions of the liver and the diverse metabolic processes occurring in the hepatocytes and sinusoidal cells. 

These six fundamental reaction types are the basis of metabolism. Remember that all six types can proceed in either direction, depending on the standard free energy for the specific reaction and the concentrations of the reactants and products inside the cell. An effective way to learn is to look for commonalities in the diverse metabolic pathways that we will be examining. There is a chemical logic that, when exposed, renders the complexity of the chemistry of living systems more manageable and reveals its elegance. 

Cells are the fundamental units of life. They are functional entities, each of which is enclosed in a semipermeable membrane that varies in composition and function both over a single cell surface and between different cell types. There are two basic forms of cell prokaryotic and eukaryotic. Prokaryotes are most noted for their small sizes and relatively simple structures. Presumably because of these traits, in addition to their remarkably rapid reproduction rates and biochemical diversity, various prokaryotic species occupy virtually every ecological niche in the biosphere. In contrast, the most conspicuous feature of the eukaryotes is their extraordinarily complex internal structure. Because eukaryotes carry out their various metabolic functions in a variety of membrane-bound organelles, they are capable of a more sophisticated intracellular metabolism. The diverse metabolic regulatory mechanisms made possible by this complexity promote two important lifestyle features required by multicellular organisms cell specialization and intercellular cooperation. Consequently, it is not surprising that the majority of eukaryotes are multicellular organisms composed of numerous types of specialized cells. 

Adrenal cortex Glucocorticoidst (cortisol, corticosterone) Diverse metabolic effects as well as inhibiting the inflammatory response... 

Electron transfers are key steps in many enzymatic reactions involving the oxidation or reduction of a bound substrate. Relevant examples include cytochrome c oxidase (O2 — 2H2O) and nitrogenase (N2 2NH3). To reinforce the claim that electron-transfer steps are of widespread importance, several other redox systems, representative of diverse metabolic processes, will be mentioned here. 

When a drug molecule gets converted into the body to an altogether different form, which may be either less or more active than the parent drug, the phenomenon is termed as biotransformation. Mostly the drug metabolism occurs in liver. In fact, a number of pathways are genuinely responsible for carrying out various diverse metabolism reactions in the body. 

Vitamins are essential organic compounds that perform numerous and diverse metabolic functions, often serving as enzymatic cofactors. With some exceptions, vitamins or their precursors must be obtained from food or supplements. The main exceptions are vitamin D, a hormone-like... 

However, this also means that chemical conditions within the mats are strongly affected by microbial metabolic activity. As light-driven systems, microbial mats experience dramatic daily fluctuations in metabolic processes, and therefore in the resulting chemical microenvironment [211,212]. It is against this backdrop of diverse metabolic capabilities and dramatically oscillating physical and chemical conditions that the cycling of H2 within microbial mats must be considered. 

The diverse metabolic activities of the liver make it susceptible to solvent induced in-jiuy, particularly from reactive intermediates which damage cellular macromolecules. The microscopic anatomy of the liver provides an explanation for this susceptibility. The basic unit of the liver is the hepatic lobule which consists of a central vein surrounded radially by sinusoids of liver cells (hepatocytes). Portal triads consisting of a hepatic artery, a hepatic vein and a bile canniliculus are located at the periphery. Liver cells closest to the vascular... 

---