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Catabolism amino acid

Fatty acids with odd numbers of carbon atoms are rare in mammals, but fairly common in plants and marine organisms. Humans and animals whose diets include these food sources metabolize odd-carbon fatty acids via the /3-oxida-tion pathway. The final product of /3-oxidation in this case is the 3-carbon pro-pionyl-CoA instead of acetyl-CoA. Three specialized enzymes then carry out the reactions that convert propionyl-CoA to succinyl-CoA, a TCA cycle intermediate. (Because propionyl-CoA is a degradation product of methionine, valine, and isoleucine, this sequence of reactions is also important in amino acid catabolism, as we shall see in Chapter 26.) The pathway involves an initial carboxylation at the a-carbon of propionyl-CoA to produce D-methylmalonyl-CoA (Figure 24.19). The reaction is catalyzed by a biotin-dependent enzyme, propionyl-CoA carboxylase. The mechanism involves ATP-driven carboxylation of biotin at Nj, followed by nucleophilic attack by the a-carbanion of propi-onyl-CoA in a stereo-specific manner. [Pg.791]

FIGURE 25.1 The citrate-malate-pyruvate shuttle provides cytosolic acetate units and reducing equivalents (electrons) for fatty acid synthesis. The shuttle collects carbon substrates, primarily from glycolysis but also from fatty acid oxidation and amino acid catabolism. Most of the reducing equivalents are glycolytic in origin. Pathways that provide carbon for fatty acid synthesis are shown in blue pathways that supply electrons for fatty acid synthesis are shown in red. [Pg.804]

Figure 29-2. Overall flow of nitrogen in amino acid catabolism. Figure 29-2. Overall flow of nitrogen in amino acid catabolism.
Lim CB et al Reduction in the rates of protein and amino acid catabolism to slow down the accumulation of endogenous ammonia a strategy potentially adopted by mudskippers during aerial exposure in constant darkness. J Exp Biol 2001 ... [Pg.248]

TRANSAMINATION TYPICALLY INITIATES AMINO ACID CATABOLISM... [Pg.249]

The catabolism of leucine, valine, and isoleucine presents many analogies to fatty acid catabolism. Metabolic disorders of branched-chain amino acid catabolism include hypervalinemia, maple syrup urine disease, intermittent branched-chain ketonuria, isovaleric acidemia, and methylmalonic aciduria. [Pg.262]

Nonessential Amino Acid Synthesis Essential Amino Acids Amino Acid Degradation Generalities of Amino Acid Catabolism Products of Amino Acid Degradation... [Pg.199]

The nitrogen contained in the amino acids is usually disposed of through the urea cycle. One of the early, if not the first, steps in amino acid catabolism involves a transamination using oxaloacetate or a-ketoglutarate as the amino-group acceptor. This converts the amino acid into a 2-keto acid, which can then be metabolized further. [Pg.201]

Liver, small intestine, muscle and kidney all participate in amino acid catabolism with the liver, under most conditions, playing the major role, but the metabolism of specific amino acids in the other three tissues is of considerable biochemical and physiological importance (see below). [Pg.159]

The amino acids falling into each category are presented in Table 8.9. The pathways in processes (i) and (ii) are described in Appendix 8.3. The combined process of deamination plus transamination illustrates important principles in amino acid catabolism. These lead to an appreciation of some of the biochemical and physiological functions of amino acids that are important in health and disease. [Pg.159]

A major aim of amino acid catabolism is removal of the a-NH2 group, which results in the formation of ammonia which is then converted to urea. The removal of the a-NH2 group for most amino acids results in the formation of a carbon-compound, which is usually an oxoacid (e.g. the oxoacid for alanine is pyruvate). [Pg.159]

Although amino acid catabolism appears complex, there are two simple but important points (principles) that help in understanding the overall plan ... [Pg.161]

Figure 8.8 The role of the Krebs cyde in the oxidation of the six common intermediates. The six short arrows indicate the positions in the cycle where the various intermediates from amino acid catabolism feed into the cycle. Eventually they are all converted to acetyl-CoA for complete oxidation by the cycle. The pathway is indicated by the broader arrows. Figure 8.8 The role of the Krebs cyde in the oxidation of the six common intermediates. The six short arrows indicate the positions in the cycle where the various intermediates from amino acid catabolism feed into the cycle. Eventually they are all converted to acetyl-CoA for complete oxidation by the cycle. The pathway is indicated by the broader arrows.
Fat synthesis The acetyl-CoA prodnced from amino acid catabolism is also a precursor for fatty acid and triacyl-glycerol synthesis, both in adipose tissne and liver (details of pathways are given in Chapter 11). Unfortnnately, the quantitative significance of this pathway is not known. It is likely to be variable and probably small in hnmans. [Pg.164]

The reaction involves formation of an imine through reaction of ammonia with the ketone, followed by reduction of this imine (see Section 7.7.1). As we noted earlier (see Section 15.1.1), nicotinamide coenzymes may also participate in imine reductions as well as aldehyde/ketone reductions, further emphasizing the imine-carbonyl analogy (see Section 7.7.1). The reverse reaction, removal of ammonia from glutamate, is also of importance in amino acid catabolism. [Pg.598]

Most of the amino acids are consumed by insect cells, with the exception of alanine which is produced however, it has been reported that alanine overflow metabolism is energetically wasteful as it is with mammalian cells [63]. The alanine production by insect cells has been interpreted as a strategy to avoid the accumulation of toxic ammonia produced from amino acid catabolism [64]. [Pg.194]

Finally amino acids are precursors for some branched aliphatic compounds such as 2-methyl-1-butanol and 3-methyl-1 -butanol that are formed during the amino acid catabolism [20]. [Pg.140]

Inherited defects of amino acid catabolism, biosynthesis, or transport have been known for many years the number of novel defects is only slowly increasing [1,3,4, 10, 12]. In this respect, cystinuria was among the first four inherited metabolic diseases described by Garrod 100 years ago. The disease with the highest impact on the community - phenylketonuria (PKU) - was discovered as early as the 1930s. Despite its early discovery, PKU remains a mysterious disease in several aspects, and patient-oriented research of this condition continues today. [Pg.54]

The pathways of amino acid catabolism are quite similar in most organisms. The focus of this chapter is on the pathways in vertebrates, because these have received the most research attention. As in carbohydrate and fatty acid catabolism, the processes of amino acid degradation converge on the central catabolic pathways, with the carbon skeletons of most amino acids finding their way to the citric acid cycle. In some cases the reaction pathways of amino acid breakdown closely parallel steps in the catabolism of fatty acids (Chapter 17). [Pg.656]

FIGURE 18-1 Overview of amino acid catabolism in mammals. The... [Pg.657]

The pathways of amino acid catabolism, taken together, normally account for only 10% to 15% of the human body s energy production these pathways are not nearly as active as glycolysis and fatty acid oxidation. Flux through these catabolic routes also varies greatly, depending on the balance between requirements for bio-... [Pg.671]

Several Enzyme Cofactors Play Important Roles in Amino Acid Catabolism... [Pg.672]


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Amino Acid Catabolism and Aminotransferases

Amino acid carbon catabolism

Amino acid carbon skeletons, catabolism

Amino acid nitrogen catabolism

Amino acid sulfur, catabolism

Amino acid, acetyl derivatives catabolism

Branched chain amino acids, catabolism

Branched chain amino acids, catabolism disorders

Catabolism aromatic amino acids

Catabolism basic amino acids

Catabolism hydroxy amino acids

Catabolism of Amino Acids Deamination

Catabolism of Amino Acids The Carbon Chains

Catabolism of amino acids

Catabolism sulfur-containing amino acids

Generalities of Amino Acid Catabolism

Nitrogen metabolism amino acid catabolism

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