Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

With amino acids, deamination decarboxylation

The NAD- and NADP-dependent dehydrogenases catalyze at least six different types of reactions simple hydride transfer, deamination of an amino acid to form an a-keto acid, oxidation of /3-hydroxy acids followed by decarboxylation of the /3-keto acid intermediate, oxidation of aldehydes, reduction of isolated double bonds, and the oxidation of carbon-nitrogen bonds (as with dihydrofolate reductase). [Pg.590]

Other than water, protein is the major constituent of meat averaging nearly 21% in heef or chicken meat, with fat varying fiom 4.6 to 11.0% in beef and fiom 2.7 to 12.6% in chickoi. The principal radiolytic reactions of aqueous solutions of aliphatic amino acids are reductive deamination and decarboxylation. Alanine yields NH3, pyruvic add, acetaldehyde, propionic acid, CO2, H2, and ethylamine (6). Sulfur-containing amino adds are espedally sensitive to ionizing radiation. Cysteine can be oxidized to cystine by the hydroxyl radical or it can react with the hydrated electron and produce... [Pg.295]

Figure 25-5 Reactions of ar-amino acids with an aldehyde, R CHO. The products are the result of decarboxylation and/or deamination the fraction of the products formed by each route is determined by the ratio of the rate of proton shift to the rate of decarboxylation of 2,... Figure 25-5 Reactions of ar-amino acids with an aldehyde, R CHO. The products are the result of decarboxylation and/or deamination the fraction of the products formed by each route is determined by the ratio of the rate of proton shift to the rate of decarboxylation of 2,...
Several of the B vitamins function as coenzymes or as precursors of coenzymes some of these have been mentioned previously. Nicotinamide adenine dinucleotide (NAD) which, in conjunction with the enzyme alcohol dehydrogenase, oxidizes ethanol to ethanal (Section 15-6C), also is the oxidant in the citric acid cycle (Section 20-10B). The precursor to NAD is the B vitamin, niacin or nicotinic acid (Section 23-2). Riboflavin (vitamin B2) is a precursor of flavin adenine nucleotide FAD, a coenzyme in redox processes rather like NAD (Section 15-6C). Another example of a coenzyme is pyri-doxal (vitamin B6), mentioned in connection with the deamination and decarboxylation of amino acids (Section 25-5C). Yet another is coenzyme A (CoASH), which is essential for metabolism and biosynthesis (Sections 18-8F, 20-10B, and 30-5A). [Pg.1267]

That amines formed from naturally occurring amino acids are partly responsible for chronic hypertension is a rather attractive hypothesis first suggested by the experiments of Holtz (35). Besides the normal metabolic enzymes of amino acids, tissues, especially kidney, liver, and brain, contain amino acid decarboxylases, some of them specific for certain amino acids, some less so. These are anaerobic enzymes. After decarboxylation, certain monoamines are deaminated by amine oxidases which are sensitive to oxygen tension. The best known of these oxidases is the enzyme of Blaschko, Richter, and Schlossmann (9), which may be a mixture of three or more (29), and which is specific for many nonsubstituted vasoactive amines found in the body, with the notable exception of histamine. [Pg.10]

When an amino acid is heated with D-glucose in a stream of oxygen at 130°, decarboxylation and deamination occur according to the following equation. Very little free ammonia can be detected, since it quickly com-... [Pg.69]

BA biosynthesis begins with the conversion of tyrosine to both dopamine and 4-hydroxyphenylacetaldehyde by a lattice of decarboxylations, orfho-hydroxylations, and deaminations.1 The aromatic amino acid decarboxylase (TYDC) that converts tyrosine and dopa to their corresponding amines has been purified, and several... [Pg.144]

Fig. 1. a-Oxidation of amino acids. Hydroxyl radical (or other reactive radical) abstracts hydrogen atom from the a-carbon. The C-centered free radical formed may react with other amino acid residues or dimerize in the absence of oxygen, which leads to protein aggregation. In die presence of oxygen the carbon-centered radical forms peroxyl radical. Reduction of peroxyl radical leads to protein hydroperoxide. Decomposition of hydroperoxide leads to formation of carbonyl compounds via either oxidative deamination or oxidative decarboxylation. Oxidation of the new carbonyl group forms a carboxyl group. [Pg.169]

Free amino acids readily form chloramines in reactions with HOC1. However, the reaction can be postponed by the presence of amino acids whose side groups have reducing properties (as is the case with cysteine, methionine, and tryptophan). Amino acid chloramines located at the a-carbon are unstable, decomposing by deamination and decarboxylation. The final stable products are ammonia, chloride, and the aldehyde respective to the amino acid carbon backbone (H12, Z4) ... [Pg.180]

Such interference falls into two classes competitive substrates and substances that either aaivate or inhibit the enzyme. With some enzymes, such as urease, the only substrate that reacts at reasonable rate is urease hence, the urease-coated electrode is specific for use (59, 165). Likewise, uricase acts almost specifically on uric acid (167), and aspartase on aspartic acid (8, 168). Others, such as penicillinase and amino oxidase, are less specific (63,169,170). Alcohol oxidase responds to methanol, ethanol, and allyl alcohol (171, 172). Hence, in using electrodes of these enzymes, the analyte must be separated if two or more are present (172). Assaying L-amino acids by using either the decarboxylative or the deaminating enzymes, each of which acts specifically on a different amino... [Pg.88]

Free radical reactions of purines with amines gave similar products to those produced in alcohol solution although deamination may also occur, probably at the post- rather than the pre-adduct stage. Whereas purine and n-propylamine afforded 6-n-propylpurine (71MI40907), adenine and caffeine produced both the 8-aminoalkyl and corresponding 9-alkyl derivatives (74MI40904). Also irradiation of 8-aminoalkylpurines in methanol furnished the 8-alkyl derivatives. Amino acids as an amine source are of special biochemical interest. They also tend to produce 8-alkylpurines by concomitant deamination and decarboxylation (69CC905). [Pg.545]

Reaction with ninhydrin Ninhydrin is a strong oxidizing agent. When a solution of amino acid is boiled with ninhydrin, the amino acid is oxidatively deaminated to produce ammonia and a ketoacid. The keto acid is decarboxylated to produce an aldehyde with one carbon atom less than the parent amino acid. The net reaction is that ninhydrin oxidatively deaminates and decarboxylates a-amino acids to C02, NH3 and an aldehyde. The reduced ninhydrin then reacts with the liberated ammonia and another molecule of intact ninhydrin to produce a purple coloured compound known as Ruhemann s purple. [Pg.147]

To date, four main types of catalytic activity have been reported in detail for thermal polyamino acids. These are (with the most studied substrates in parentheses) hydrolyses (p-nitrophenyl acetate, p-nitro-phenyl phosphate, ATP), decarboxylations (OAA, glucuronic acid, pyruvic acid), and aminations (a-ketoglutaric acid, OAA, pyruvic acid, phenylpyruvic acid). The fourth type is a deamination reaction yielding a-ketoglutaric acid (51). For some of the actions of the thermal polymers the products are identified quantitatively, and the kinds of amino acid side chain necessary for activity in the polymer elucidated. In others, products have yet to be fully identified. The activities of thermal polyamino acids are manifest on substrates which range from chemically labile to relatively stable. [Pg.409]

It may not, however be necessary for decarboxylation of the amino acid to occur. A condensation with the amino acid similar to that above wmuld give the same result if decarboxylation occurred after condensation. Similarly an aldehyde component need not be present as such a potential aldehyde, such as a keto or imino acid, also condenses readily (e.g., 334, 337). Again the same product is obtained by subsequent decarboxylation. Transamination is known to occur in plants (e.g., 931) and the occurrence of keto acids is to be expected. Both amino and keto acids could of course be formed from the amino acid by oxidative deamination. [Pg.118]

The various decomposition reactions outlined in the preceeding section would remove amino acid from the buffered solutions, and if these reactions were significant compared with the k values, Equation 9 would have to be modified. Since the racemization was studied under anaerobic conditions, the decarboxylation and deamination reactions are the only important amino acid decomposition reactions. With the exception of the deamination of aspartic acid, the decomposition rates of the other amino acids studied were negligible compared with the racemization rate of the amino acid. Integration of Equation 9 yields... [Pg.326]


See other pages where With amino acids, deamination decarboxylation is mentioned: [Pg.790]    [Pg.272]    [Pg.73]    [Pg.230]    [Pg.365]    [Pg.789]    [Pg.18]    [Pg.103]    [Pg.196]    [Pg.155]    [Pg.138]    [Pg.829]    [Pg.271]    [Pg.528]    [Pg.404]    [Pg.327]    [Pg.103]    [Pg.1386]    [Pg.1223]    [Pg.163]    [Pg.275]    [Pg.84]    [Pg.857]    [Pg.214]    [Pg.278]    [Pg.432]    [Pg.13]    [Pg.155]    [Pg.3548]    [Pg.136]    [Pg.12]    [Pg.261]    [Pg.7]    [Pg.236]   
See also in sourсe #XX -- [ Pg.1223 ]




SEARCH



Amino acids deamination

Amino acids decarboxylation

With amino acids, deamination

© 2024 chempedia.info