Kidney fatty acid activating enzymes

The acyl CoA synthetase that activates long-chain fatty acids, 12 to 20 carbons in length, is present in three locations in the cell the endoplasmic reticulum, outer mitochondrial membranes, and peroxisomal membranes (Table 23.1). This enzyme has no activity toward C22 or longer fatty acids, and little activity below C12. In contrast, the synthetase for activation of very-long-chain fatty acids is present in peroxisomes, and the medium-chain-length fatty acid activating enzyme is present only in the mitochondrial matrix of liver and kidney cells. 

The oxidation of aciy lic acid can be rationalized in terms of the endogenous catabolism of propionic acid, in which acrylyl coenzyme A is an intermediate. This pathway is analogous with fatty acid 3-oxidation, common to all species and, unlike the corresponding pathway in plants, does not involve vitamin 8,2. 3-Hydroxypropionic acid has been found as an intennediate in the metabolism of acrylic acid in vitro in rat liver and mitochondria (Finch Frederick, 1992). The CO2 excreted derives from the carboxyl carbon, while carbon atoms 2 and 3 are converted to acetyl coenzyme A, which participates in a variety of reactions. The oxidation of acrylic acid is catalysed by enzymes in a variety of tissues (Black Finch, 1995). In mice, the greatest activity was found in kidney, which was five times more active than liver and 50 times more active than skin (Black et al., 1993). 

Metabolic processes speed up appreciably under the influence of caffeine. Fatty acids are released into the blood, and a general increase in metabolism is evident as there is increased muscle activity, raised temperature, or both. More calcium is made available through caffeine s action in the muscles for contraction, but this effect is evident only at caffeine doses higher than people commonly use. Gut motility and secretion increase with a release of stomach acid and digestive enzymes. Urination is also stimulated caffeine directly affects the kidneys, cutting into their ability to reabsorb electrolytes and water. For every cup of coffee or two to three cans of caffeinated soft drink consumed, about 5 mg of calcium is lost in the urine. 

Table VI summarizes total GSH-Px activity toward LHP and 15-HPETE in tissues from rats fed on vitamin E and/or Se deficient diets. GSH-Px activity toward fatty acid hydroperoxides was reduced markedly in liver and lung under Se-deficient states whereas kidney enzyme levels were only marginally affected. It should be noted that these total enzyme activities were contributed by both Se-GSH-Px and non-Se GSH-Px in crude cytosols of Se supplemented animals. However, in Se-deficient...

Essential fatty acids (EFAs) are essential for the survival of humans and other mammals they cannot be synthesized in the body and, hence, have to be obtained in our diet and, thus, are essential (1-4). EFAs are an important constituent of cell membranes and confer on membranes properties of fluidity thus, they determine and influence the behavior of membrane-bound enzymes and receptors. Two types of naturally occurring EFAs exist in the body the oo-6 series derived from linoleic acid (LA, 18 2) and the oo-3 series derived from a-linolenic acid (ALA, 18 3). Both the 00-6 and the oo-3 series are metabolized by the same set of enzymes to their respective long-chain metabohtes. Although some functions of EFAs require their conversion to eicosanoids and other products, in most instances the fatty acids themselves are active. The longer-chain metabolites of LA and ALA regulate membrane function and are of major importance in the brain, retina, liver, kidney, adrenal glands, and gonads. 

Mercury is a reactive element and its toxicity is probably due to interaction with proteins. Mercury has a particular affinity for sulphydryl groups in proteins and consequently is an inhibitor of various enzymes such as membrane ATPase, which are sulphydryl dependent. It can also react with amino, phosphoryl and carboxyl groups. Brain pyruvate metabolism is known to be inhibited by mercury, as are lactate dehydrogenase and fatty acid synthetase. The accumulation of mercury in lysosomes increases the activity of lysomal acid phosphatase which may be a cause of toxicity as lysosomal damage releases various hydrolytic enzymes into the cell, which can then cause cellular damage. Mercury accumulates in the kidney and is believed to cause uncoupling of oxidative phsophorylation in the mitochondria of the kidney cells. Thus, a number of mitochondrial enzymes are inhibited by Hg2+. These effects on the mitochondria will lead to a reduction of respiratory control in the renal cells and their functions such as solute reabsorption, will be compromised. 

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