Role in cell metabolism

The extreme toxicity of FA is determined by its similarity to acetate, which has a central role in cell metabolism. FA enzymatically condenses with CoA-SH to produce... 

Vitamin E plays an important role in cell metabolism as an antioxidant for the elimination of reactive oxygen intermediates. Subsequent to intestinal resorption, vitamin E is transported in chylomicrons into the liver, from where it reaches other organs together with VLDL. Vitamin E deficiency is observed in chronic liver diseases caused by alcohol, Wilson s disease, haemochromatosis and abetalipoproteinaemia. In vitamin E deficiency, neurologic disturbances (areflexia, dysbasia, ocular palsy, reduced perception of vibration) occur haemolysis can likewise be induced or become more pronounced due to epoxide formation of unsaturated fatty acids within the erythrocyte membranes. 

Friedel, H.A., Goa, K.L., Benfield, R S-adenosyl-L-methionine. A review of its pharmacological properties and therapeutic potential in liver dysfunktion and affective disorders in relation to its pl siological role in cell metabolism. Drugs 1989 38 389-416... 

The presence of both synthesizing and degrading enzymes in cells, together with the established rapid turnover of many of the ADP-ribose residues, supports the concept that ADP-ribosylation is, indeed, a reversible process which plays a regulatory role in cell metabolism. 

Poly(ADP-ribose) polymerase is activated by DNA strand breaks and this property is central to its regulatory role in cell metabolism. The enzyme is tightly bound to chromatin where it ADP-ribosylates chromosomal proteins including histones, nonhistones, and itself (automodification), and its activity influences and is influenced by chromatin structural changes. These properties point to a funda-... 

Introduction and Rationale. DHFR is an ideal system to study for a number of reasons. The catalytic properties of DHFR are such that under normal physiologic conditions and with the NADPH cofactor bound, 7,8-dihydrofolate (DHF) is reduced to 5,6,7,8-tetrahydrofolate (THF) (7). Thus DHFR plays an important role in cell metabolism by maintaining a supply of THF. THF is used by the cell as both a cofactor and in substrate quantities in the synthesis of deoxythymidine. By inhibiting the production of THF, deoxythymidine synthesis is curtailed, nucleic add replication comes to a halt, and cell proliferation ceases. It is this biochemical cascade which supplies the pharmacological and chemotherapeutic applications of inhibitors to DHFR. 

Newsholme P, Procopio J, Lima, MMR, Pithon-Curu TC, Cori R. Glutamine and glutamate— their central role in cell metabolism and function. Cell Biochem Funct 2003 21 1-9. 

The early view that mitochondria might be autonomous (i.e., capable of independent synthesis of the majority of their own proteins) can safely be disregarded. In fact, all evidence shows that only very few mitochondrial proteins are coded for by the mitochondrial genome. The majority of proteins are synthesized outside the mitochondria and then transported into the organelles where the membrane structures are assembled. The questions then arise, which proteins are regulated by the mitochondrial genome, and do they play a key role in cell metabolism ... 

Vitamin B plays important roles in cell metabolism. Vitamin B actually consists of eight chemically distinct biologically active agents that function as coenzymes. Pyridoxine, pyridoxal, and pyridoxamine or pyridoxine hydrochloride can all be called vitamin B6 as they are all converted to the active form. Pyridoxine is involved in the metabolism of amino acids and lipids. A vitamin B6-dependent enzyme model... 

The extreme toxicity of FA is determined by its similarity to acetate, which plays a central role in cell metabolism. FA enzymatically condenses with CoA-SH to produce fluoroacetyl-CoA, which replaces acetyl-CoA entering to the TCA cycle and produces FC. TTie latter reacts with aconitase and blocks TCA cycle. Energy production is reduced, as well as the concentration of metabolites generated distally to aconitase. Of these, 2-Oxoglutarate is the most important, being a precursor... 

CMAllENGtl The citric acid cycle is a series of biological reactions that plays a central role in cell metabolism. The cycle includes dehydration reactions of both malic and citric acids, yielding fumaric and aconitic acids, respectively (all common names). Both proceed strictly by enzyme-catalyzed anti elimination mechanisms. 

Glial cells are cells within the central or peripheral nervous system which are not immediately involved in information processing. Glial cells play an mportant role in the metabolic homeostasis of brain tissue and in nervous system development. 

Glutathione has other important functions in human cells apart from its role in xenobiotic metabolism. 

Rice bran is the richest natural source of B-complex vitamins. Considerable amounts of thiamin (Bl), riboflavin (B2), niacin (B3), pantothenic acid (B5) and pyridoxin (B6) are available in rice bran (Table 17.1). Thiamin (Bl) is central to carbohydrate metabolism and kreb s cycle function. Niacin (B3) also plays a key role in carbohydrate metabolism for the synthesis of GTF (Glucose Tolerance Factor). As a pre-cursor to NAD (nicotinamide adenine dinucleotide-oxidized form), it is an important metabolite concerned with intracellular energy production. It prevents the depletion of NAD in the pancreatic beta cells. It also promotes healthy cholesterol levels not only by decreasing LDL-C but also by improving HDL-C. It is the safest nutritional approach to normalizing cholesterol levels. Pyridoxine (B6) helps to regulate blood glucose levels, prevents peripheral neuropathy in diabetics and improves the immune function. 

Glucose phosphate isomerase (GPI) catalyzes the reversible interconversion of glucose-6-phosphate and fructose-6-phosphate. GPI plays an essential role in carbohydrate metabolism in all cells of the body. The substrates of this enzyme, ffuc-... 

Insulin also plays a role in fat metabolism. In humans, most fatty acid synthesis takes place in the liver. The mechanism of action of insulin involves directing excess nutrient molecules toward metabolic pathways leading to fat synthesis. These fatty acids are then transported to storage sites, predominantly adipose tissue. Finally, insulin stimulates the uptake of amino acids into cells where they are incorporated into proteins. 

The authors chose pyruvic acid as their model compound this C3 molecule plays a central role in the metabolism of living cells. It was recently synthesized for the first time under hydrothermal conditions (Cody et al., 2000). Hazen and Deamer carried out their experiments at pressures and temperatures similar to those in hydrothermal systems (but not chosen to simulate such systems). The non-enzymatic reactions, which took place in relatively concentrated aqueous solutions, were intended to identify the subsequent self-selection and self-organisation potential of prebiotic molecular species. A considerable series of complex organic molecules was tentatively identified, such as methoxy- or methyl-substituted methyl benzoates or 2, 3, 4-trimethyl-2-cyclopenten-l-one, to name only a few. In particular, polymerisation products of pyruvic acid, and products of consecutive reactions such as decarboxylation and cycloaddition, were observed the expected tar fraction was not found, but water-soluble components were found as well as a chloroform-soluble fraction. The latter showed similarities to chloroform-soluble compounds from the Murchison carbonaceous chondrite (Hazen and Deamer, 2007). 

Several kinetic parameters can be measured on different experimental systems to account for the interaction of a compound with CYPs. For example when studying the metabolic stability of a compound, it could be measured in a recombinant CYP system, in human liver microsomes, in hepatocytes and so on. Each system increases in biological complexity. Although in the recombinant CYP system only the cytochrome under consideration is studied, in the case of the human liver microsomes, there is a pool of enzyme present that includes several CYPs, and finally in the hepatocyte cell system, metabolizing enzymes play an important role in the metabolic compound stability. In addition, transport systems are also present that could involve recirculation or other transport phenomena. The more complex the experimental system, the more difficult it is to extract information on the protein/ligand interaction, albeit it is closer to the in vivo real situation and therefore to the mechanism that is actually working in the body. 

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