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Oxidative Deamination Reactions

Oxidative N-. 0-. and S-dcalkylation as well as oxidative deamination reactions fall under this mechanistic pathway. [Pg.84]

In general, dealkylation of secondary amines is believed to occur before oxidative deamination. Some evidence indicate ., however, that this may not always be true. Direct deamination of the secondary amine also has occurred. For uampic. in addition to uncleigoing deamination through its dcsisopropyl primary amine metabolite, propranolol can undergo a direct oxidative deamination reaction (also by a-carbon hydroxylalion) to yield the aldehyde metabolite and Mpropylamine (Fig. 4-9). How much direct oxidative deamination contributes to the metabolism of. secondary amines remains unclear. [Pg.89]

It is difficult to estimate what the rate of the metal ion catalyzed oxidative deamination reaction of amino acids would be in natural waters. Hamilton and Revesz (30) found that the rate of oxidation of alanine in the presence of pyridoxal and manganese ions was inhibited by EDTA. Since metal ions in natural waters can be complexed by a variety of organic and inorganic compounds, their effectiveness in catalyzing the oxidative deamination of amino acids may be reduced. Also, the fraction of dissolved amino acids which would be complexed by metal ions at the pH and metal ion and amino acid concentrations found in natural waters must be considered. At neutral pH, where the amino group of the amino acid is protonated, the fraction of the amino acid that would be in the form of the metal ion complex depends upon the equilibrium constant for the formation of the complex and the pK of the amino proton of the amino acid. The reactions for the formation of the Cu2+-alanine complexes can be written as... [Pg.321]

Oxidative deamination reactions of free -NH2 groups which proceed via the formation of imino acids and their hydrolysis and lead to the formation of ketoacyl peptides or to the forming of the C-terminal amino acid according to the summary scheme... [Pg.475]

In addition to the above mentioned oxidative deamination reactions and Garrisons cleavage of the peptide bond, oxidation and degradation reactions also take place in the remaining amino acid chains, including the benzene nucleus of Phe, as can be inferred from the presence of dialdehydes which have been found in irradiated solutions of polymyxin. As a result of these reactions the content of individual amino acids in the hydrolysates of irradiated solutions is successively lower, the decrease being largest for Phe, Leu, and for methyloctanoic acid. [Pg.480]

Co", Cr", Cu", Pd" and Pt" accelerate the racemization rates of amino acids. The mechanisms are not always as simple as that outlined above for Co". Thus, with [Cu(L-AlaO)2] it has been known for some time that the rate of racemization was faster than that for H-D exchange under the same conditions. It was subsequently shown that at high pH, with O2 present, pyruvate was formed from an oxidative deamination reaction which further catalyzed the racemization rate through formation of a Schiff base intermediate (16). This combination of carbanion and Schiff base intermediates was further confirmed by studies on the Zn" complex. Contrary to earlier reports it has now been shovra that Ni" actually retards the racemization rates of amino acids. ... [Pg.1403]

In the oxidative deamination reaction, the enzyme was active toward N-[l-D-(carboxyl)ethyl]-L-methionine, N-[l-D-(carboxyl)ethyl]-L-phenylalanine, etc. The substrate specificity for amino donors of ODH in the reductive secondary amine-forming reaction was examined with pyruvate as a fixed amino acceptor [15,24]. The enzyme utilized L-norvaline, L-2-aminobutyric acid, L-norleucine, P-chloro-L-alanine, o-acetyl-L-serine, L-methionine, L-isoleucine, L-valine, L-phenylalanine, L-homophenylalanine, L-leucine, L-alanine, etc. 3-Aminobutyric acid and L-phenylalaninol also acted as substrates for the enzyme. Other amino compounds, such as P-amino acids, amino acid esters and amides, amino alcohols, organic amines, hydroxylamines, and hydrazines, were inactive as substrates. Pyruvate, oxaloacetate, glyoxylate, and a-ketobutyrate were good amino acceptors. We named the enzyme as opine... [Pg.22]

A possible explanation for this anomaly comes from the results of Garland and Dennis (1977). The reductive amination reaction of the pea stem mitochondrial GDH was activated by Ca " and Mn +, the concentrations for half-maximal activity being 9 /xM and 480 /aM, respectively. High concentrations of Ca did not inhibit the enzyme. Zn " activated the reaction at low concentrations, but concentrations above 2 mM were inhibitory. Cs only slightly inhibited the oxidative deamination reaction. [Pg.292]

Pahlich and Joy (1971) have presented evidence for aggregation/ disaggregation phenomena with the NAD-linked GDH from pea roots. Certain pretreatments of the enzyme can change its relative ability to perform the reductive amination and oxidative deamination reactions. Treatments which favor NADH-dependent activity are Tris buffer, Ca " and low concentrations of dioxane. These treatments simultaneously decrease the NAD-dependent activity, while phosphate buffer increases NAD-dependent activity and decreases NADH activity. It was proposed that the pea root enzyme may exist in two interconvertible catalytically active forms, one predomi-... [Pg.292]

Oxidative Deamination Reactions. The enzymes amine oxidases (AOs) catalyze the oxidative deamination of a wide range of biogenic amines. There are two classes of AOs copper AOs and flavin-containing AOs. Copper-containing AOs catalyze the oxidation of primary amines to aldehydes, with the subsequent release of ammonia and hydrogen peroxide, which requires one copper ion per subunit and topaquinone (TPQ) (2,4,5-trihydroxyphenylalanine) as cofactor (Figure 1.50). [Pg.38]

A7 Complete the following oxidative deamination reaction ... [Pg.832]

The ophio-Z-amino acid oxidase was discovered in the venom of Vipera aspis, V. libetina, V. latastei, BorUirops atrox, Naja sp., etc. and was studied by Zeller and Maritz (146,147). It is differentiated from Z>amino acid oxidase of tissues of higher animals by its inability to oxidize Z-pro-line, Z-oxyproline, and ZV-methyl-Z-leucine and its insensitivity toward ammonium sulfate (148). Otherwise, it produces the same oxidative deamination reactions and acts particularly on Z-methionine. [Pg.375]


See other pages where Oxidative Deamination Reactions is mentioned: [Pg.124]    [Pg.757]    [Pg.305]    [Pg.342]    [Pg.479]    [Pg.482]    [Pg.468]    [Pg.116]    [Pg.286]    [Pg.287]    [Pg.469]    [Pg.6]    [Pg.84]    [Pg.374]    [Pg.389]   
See also in sourсe #XX -- [ Pg.38 ]




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Deamination reactions

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