Ammonia amino acids derived from

Figure 18-2a provides an overview of the catabolic pathways of ammonia and amino groups in vertebrates. Amino acids derived from dietary protein are the source of most amino groups. Most amino acids are metabolized in the liver. Some of the ammonia generated in this... 

Reduced nitrogen enters the human body as dietary free amino acids, protein, and the ammonia produced by intestinal tract bacteria. Amino acids derived from dietary proteins are the main source of amino groups. In which metabolic circumstances, amino acids in body can undergo oxidative degradation ... 

Renal tubular cells are able to generate ammonia from glutamine and other amino acids derived from muscle and hver cells according to the following reaction ... 

Amino acids derived from dietary or body proteins are also potential fuels that can be oxidized to acetyl CoA, or converted to glucose and then oxidized (see Fig. 2). These oxidation pathways, like those of fatty acids, generate NADH or FAD(2H). Ammonia, which can be formed during amino acid oxidation, is toxic. It is therefore converted to urea in the liver and excreted in the urine. There are more than 20 different amino acids, each with a somewhat different pathway for oxidation of the carbon skeleton and conversion of its nitrogen to urea. Because of the complexity of amino acid metabolism, use of amino acids as fuels is considered separately in Section Seven, Nitrogen Metabolism. 

Another catalytic application emanating from the Hieber base reaction was developed by Reppe and Vetter [108]. They showed that 1-propanol 126 could be generated by treatment of ethylene 125 with catalytic amounts of Fe(CO)5 78 under CO-pressure and basic reaction conditions (Scheme 33). Thereby, trimethylamine and V-alkylated amino acid derivatives mrned out to be optimal bases for this reaction. Like ethylene 125, propylene could be transferred mainly to 1-butanol diolefins like butadiene only reacted to monoalcohols. By employing these reaction conditions to olefins in the presence of ammonia, primary or secondary amines, mono-, di-, and trialkylamines were obtained whose alkyl chains were elongated with one carbon atom, compared to the olefins. 

The addition of ammonia to the variety of acids derivable from either the breakdown of glucose, glycolysis, or of the pentose shunt reaction products, ribose and NADPH, and from the citrate cycle, gives the amino acids (see Table 4.7 and Figure 4.4) Polymerisation of amino acids in cells gives proteins. In some of the amino acids sulfur and selenium can be incorporated easily. We assume NH3 was present. (Note that Se is in a coded amino acid not in Table 4.7.) Some selective metal-binding properties can be seen in Table 4.7, but amino acid carboxylates can bind all. 

In the fed state, when there is abundant protein and carbohydrate, dietary protein is hydrolyzed to amino acids. Those amino acids not required for protein synthesis are converted to 2-oxoacids by the aminotransferases. The 2-oxoacids are then converted into lipids and carbohydrate for storage. Glutamate dehydrogenase catalyzes the formation of ammonia from the excess amino groups derived from the amino acids this ammonia is excreted as urea. 

Addition Reaction. The double bond of dehydroalanine and e-methyl dehydroalanine formed by the e-elimination reaction (Equation 6) is very reactive with nucleophiles in the solution. These may be added nucleophiles such as sulfite (44). sulfide (42), cysteine and other sulfhydryl compounds (20,47), amines such as a-N-acetyl lysine (47 ) or ammonia (48). Or the nucleophiles may be contributed by the side chains of amino acid residues, such as lysine, cysteine, histidine or tryptophan, in the protein undergoing reaction in alkaline solution. Some of these reactions are shown in Figure 1. Friedman (38) has postulated a number of additional compounds, including stereo-isomers for those shown in Figure 1, as well as those compounds formed from the reaction of B-methyldehydroalanine (from 6 elimination of threonine). He has also suggested a systematic nomenclature for these new amino acid derivatives (38). As pointed out by Friedman the stereochemistry can be complicated because of the number of asymmetric carbon atoms (two to three depending on derivative) possible. 

Those alkaloids formed by introducing nitrogen (in the form of an amine or ammonia, etc.) into preformed terpenoid moieties are known as terpenoid alkaloids. In these alkaloids, the origin of the nitrogen in the molecule is not through the incorporation of the carbon skeleton of an amino acid. Similarly, alkaloids derived through the polyketide pathway, and the alkaloids derived from a C5-C1 unit, which are described in the following chapters, are also not directly amino acid derived. 

In general, silages of this type are characterised by having high pH values, usually within the range 5.0-7.0. The main fermentation acid present is either acetic or butyric acid. Lactic acid and residual water-soluble carbohydrates are present in low concentrations or are absent. The ammonia nitrogen levels are usually above 200 g/kg TN. This ammonia, which is derived from the catabolism of amino acids, is accompanied by other degradation products such as amines and various keto acids and fatty acids (see Table 19.1). 

This approach is used to prepare many substituted aminopropenoic acid derivatives from the appropriate P-keto-ester. -H73 in reaction 1,1.126 reacted with ammonia in ethanol to give ethyl 3-amino-4-methylpent-2-enoate, 1.127P p-Keto-esters can also be condensed with nitriles to give the corresponding alkenyl... 

A "simple" reaction of ammonia and an alkyl halide can sometimes give unusual results. Treatment of 7.62 with ammonia, followed by treatment with acid, led to a product with the amine group distal to the carboxyl group. The alkene moiety also "migrated" into conjugation with the acid (derived from hydrolysis of the cyano group). In this reaction, 7.62 was converted to 4-amino-1-cyclohexene carboxylic acid (7.63).31... 

The Strecker [1] and Bucherer-Bergs [2] reactions are the most important strategies and powerful tools for the synthesis of a-amino acids from a carbonyl compound and cyanide. The classical first approach uses ammonium hydroxide and potassium cyanide to obtain the corresponding aminonitrile compound 1, whereas the second one is a four-component condensation between an aldehyde or ketone derivative reacting with potassium cyanide and ammonium carbonate as source of ammonia and carbon dioxide affording hydan-toin componnds 2 [3], In both cases, final hydrolysis would deliver the corresponding o,a-disubstituted a-amino acid derivatives 3 (Scheme 10.1) [4],... 

Urea is the form in which amino groups derived from amino acids are disposed of from the body. One nitrogen atom of the urea molecule comes from free ammonia, the other from aspartate. All but two of the reactions of the cycle occur in the cytosol of liver hepatocytes the other two occur in the mitochondria. Urea is transported to the kidney for excretion into the urine. Urea is produced by the liver even during starvation, as skeletal muscle proteins are broken down to release amino acids to act as gluconeogenic precursors. The amino group is removed from these amino acids and converted into urea, which is then excreted in the urine. 

In the case of the bases derived from quaternary heterocyclic ammonium salts, the carbinolamines (5) can react as cyclic aldehyde-ammonias with many reagents with which the amino-aldehyde (7) could react. However, reactions of the carbinolamines which are not characteristic of amino-aldehydes are also known. Carbinolamines can easily be reconverted into the quaternary salts by the action of dilute acids, and they form alkyl ethers very easily with alcohols. If these last reactions do not occur, then this is convincing evidence for the base possessing the amino-aldehyde structure. However, if these reactions do occur this does not provide unambiguous confirmation of the carbinolamine structure. They are also given by the bi-molecular ethers (8), and, in the case of a tautomeric equilibrium... 

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