Amino group transfer

Amino acids for infusion solutions are produced by amino group transfer reactions applying transaminases. Here, a major drawback is the equilibrium conversion of only 50%. Therefore,... 

Transfer, Glyeosyl Transfer, Amino Group Transfer, Other Transferases... 

Amino group transfer Amino acid Amine... 

Many of the reactions described so far point to the concept of waste nitrogen. What happens to the ammonium ions discharged during catabolism of the various amino acids What happens to the amino groups transferred from various amino adds to oxaloacetic acid, yielding aspartate The ammonium ions and excess amino groups, carried in the form of aspartate, are handled in the following marmer. They are incorporated into a small, water-soluble molecule known as... 

When one of the substrates is water (i.e., when the process is one of hydrolysis), with the reaction taking place in aqueous solution, only a fraction of the total number of water molecules present participates in the reaction. The small change in the concentration of water has no effect on the rate of reaction and these pseudo-one substrate reactions are described by one-substi ate kinetics. More generally the concentrations of both substrates may be variable, and both may affect the rate of reaction. Among the bisubstrate reactions important in clinical enzymology are the reactions catalyzed by dehydrogenases, in which the second substrate is a specific coenzyme, such as the oxidized or reduced forms of nicotinamide adenine dinucleotide, (NADH), or nicotinamide adenine dinucleotide phosphate, (NADPH), and the amino-group transfers catalyzed by the aminotransferases. 

Pyridoxine (B6) Pyridoxal phosphate Amino group transfer... 

Although the enzyme that catalyzes this reaction, alanine aminotransferase, has cytoplasmic and mitochondrial forms, the majority of its activity has been found in the cytoplasm. Recall that the alanine cycle (Chapter 8) contributes to the maintenance of blood glucose. BCAA are the ultimate source of many of the amino groups transferred from glutamate in the alanine cycle (Figure 8.9). 

Fig. 3.18 Amino group transfer (animation ofct-ketoglutarate after Woodall et al. 1996). P = inorganic phosphorus.

Aspartate aminotransferase catalyzes amino group transfer between acidic amino... 

The amino-group transfer is from L-glutamic acid and involves enzyme-... 

The basic mechanism of this reaction is thus closely similar to those of other amino-group transfers and it exploits the ketonic character of the 4-oxo-sugar intermediate. 

The availabihty of a broad variety of oo-TAs together with efficient techniques to shift the equilibrium allows the biocatalytic synthesis of amines from the corresponding ketones via amino-group transfer. The potential of this protocol is demonstrated by a selection of amines, which can be obtained in nonracemic form by using the most prominent oo-transaminases (Scheme 2.227). 

Certain group-transfer reactions are common to many aspects of nucleotide metabolism. These include phosphoryl group transfers which generate the nucleoside polyphosphates found in the cells (Chapter 4), and one-carbon and amino group transfers by which purine and pyrimidine rings are formed and interconverted (Chapter 5). Finally, the formation of the ribose moiety of nucleotides is considered (Chapter 6) to conclude Part I. 

In addition to the transphosphorylation reactions discussed in Chapter 4, there are several general types of carbon and nitrogen transfer reactions which also occur in purine and pyrimidine nucleotide biosynthesis and interconversion. Among these are one-carbon and phosphoribosyl transfer reactions, amino group transfer from glutamine and aspartate, and amide syntheses. In most of these processes carbon-nitrogen bonds... 

Boyer, P. D. (ed.) The Enzymes, Vol. 9, Group Transfer, Part B, Phosphoryl Transfer, One-Carbon Group Transfer, Glycosyl Transfer, Amino Group Transfer, Other Transferases. Academic Press, New York 1973... 

The conversion of pyridoxal to pyridoxamine in heat-sterilized media was confirmed to be due to the reaction of pyridoxal with amino acids (Snell 1945). This was the first discovery of nonenzymatic transamination. The transamination reaction in animal tissues was first discovered in 1937 by Alexander Braunstein and associates as an amino group transfer between glutamate and alanine in pigeon muscle extract (Braunstein 1939). Irwin Gunsalus and associates showed that the tyrosine decarboxylase activity of S. faecalis was... 

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