FAT SYNTHESIS AND DEGRADATION

Fatty Acid Synthesis Function Fatty Acid Synthesis Location Fatty Acid Synthesis Connections Fatty Acid Synthesis Regulation Fatty Acid Synthesis ATP Costs (for Cig) 

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Exploring carbohydrates, from the simple to the complex Observing the reactions, synthesis, and degradation of monosaccharides Checking out lipids, specifically fats... 

Coenzyme A is necessary for the activation, synthesis, and degradation of fatly acids. Synthesis of cholesterol and ultimately the production of steroid hormones are also coenzymc A dependent. 

Long-term control is mediated by changes in the rates of synthesis and degradation of the enzymes participating in fatty acid synthesis. Animals that have fasted and are then fed high-carbohydrate, low-fat diets show marked increases in their amounts of acetyl CoA carboxylase and fatty acid synthase within a few days. This type of regulation is known as... 

Production of MAGs reported so far was reviewed based on the reactions (hydrolysis, esterification, and transesterification) catalyzed by lipases from the viewpoint of industrial production. In addition, application of the reactions to oil processing and regiospecific analysis of TAGs has been introduced. There is increased attention to lipases in the food industries and in the field of synthesis and degradation of unstable oil- and fat-related compounds. We hope this review is useful for those who intend to use lipases for oil and fat processing. 

The chemistry and biochemistry of the tocopherylquinones and tocopherols has been recently reviewed in some detail. The first recognized function of vitamin E was as an antisterility factor for the laboratory rat. However, it is now known to have multiple functions in vivo. For example, it is required for the maintenance of structural and functional integrity of skeletal, cardiac, and smooth muscle and, in some animals, the peripheral vascular system. Tocopherols also function as intracellular antioxidants, particularly with respect to the stabilization of ingested fats and perhaps products arising in the metabolic synthesis and degradation of lipids. It has also been proposed that the tocopherylquinones may have some functional role in electron transport systems. 

Fat synthesis in the liver (right). Fatty acids and fats are mainly synthesized in the liver and in adipose tissue, as well as in the kidneys, lungs, and mammary glands. Fatty acid biosynthesis occurs in the cytoplasm—in contrast to fatty acid degradation. The most important precursor is glucose, but certain amino acids can also be used. 

Il.f.l.1. Insulins. Insulin is the most effective of diabetes medications. Insulin has profound effects on carbohydrate, protein, fat metabolism and electrolytes. It has anabolic and anticatabolic actions. In a state of insulin deficiency, glycogenesis, glucose transport, protein synthesis, triglyceride synthesis, LPL activity in adipose tissue, cellular potassium uptake all decrease on the other hand, gluconeogene-sis, glycogenolysis, protein degradation, ketogene-sis, lipolysis increase. 

To meet these changing circumstances, the liver has remarkable metabolic flexibility. For example, when the diet is rich in protein, hepatocytes supply themselves with high levels of enzymes for amino acid catabolism and gluconeogenesis. Within hours after a shift to a high-carbohydrate diet, the levels of these enzymes begin to drop and the hepatocytes increase their synthesis of enzymes essential to carbohydrate metabolism and fat synthesis. Liver enzymes turn over (are synthesized and degraded) at live to ten times the rate of enzyme turnover in other tissues, such as muscle. Extrahepatic... 

Before closing we should point out that, over an extended period, dietary conditions can alter the levels of enzymes involved in fatty acid metabolism. For example, the concentrations of fatty acid synthase and acetyl-CoA carboxylase in rat liver are reduced four- to fivefold after fasting. When a rat is fed a fat-free diet, the concentration of fatty acid synthase is 14-fold higher than in a rat maintained on standard rat chow diet. Current evidence indicates that the levels of these enzymes are governed by the rate of enzyme synthesis, not degradation. It appears that synthesis of the enzyme, in turn, is controlled by the rate of transcription of DNA into mRNA. A question of current interest is how this transcription of DNA is regulated. 

Fatty acid synthesis occurs in the cytoplasm, whereas fatty acid oxidation occurs in mitochondria. As mentioned previously, physicians are not so much interested in the intracellular localization of reactions as they are in the distribution of the reactions in the various organ systems. Lipids are such important components of cell membranes that the processes of lipid biosynthesis and degradation are near universal. Lipid" storage as triglycerides, however, is mainly a function of fat cells. 

The data in Figure 7.16 reveal an increase in serum leptin in obese persons, These data could moan an increase in leptin production (by fat tissue), or a decline in ieptin uptake and degradation (by other tissues). Please devise an experiment for assessing changes in the rate of leptin synthesis- Flease design a test for measuring changes in leptin uptake (uptake from blood). 

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