Glutamic acid transamination

Effect of Different h-Keto Acids on Glutamine and Glutamic Acid Transamination with Rat Liver Preparations ... 

L Glutamic acid is not an essential ammo acid It need not be present m the diet because animals can biosynthesize it from sources of a ketoglutaric acid It is however a key intermediate m the biosynthesis of other ammo acids by a process known as transamination L Alanine for example is formed from pyruvic acid by transamination from L glutamic acid... 

In transamination an amine group is transferred from L glutamic acid to pyruvic acid An outline of the mechanism of transamination is presented m Figure 27 4... 

Vitamin Ba (pyridoxine, pyridoxal, pyridoxamine) like nicotinic acid is a pyridine derivative. Its phosphorylated form is the coenzyme in enzymes that decarboxylate amino acids, e.g., tyrosine, arginine, glycine, glutamic acid, and dihydroxyphenylalanine. Vitamin B participates as coenzyme in various transaminations. It also functions in the conversion of tryptophan to nicotinic acid and amide. It is generally concerned with protein metabolism, e.g., the vitamin B8 requirement is increased in rats during increased protein intake. Vitamin B6 is also involved in the formation of unsaturated fatty acids. 

Unnatural Amino Acids by Enzymatic Transamination Synthesis of Glutamic Acid Analogues with Aspartate Aminotransferase... 

Helaine, V., Rossi, J., Gefflaut, T., Alaux, S. and Bolte, J., Synthesis of 4,4-disubstituted l-glutamic acids by enzymatic transamination. Adv. Synth. Catal., 2001, 343, 692-697. 

The rest of the amino acids are synthesized by transamination reactions in which the amino group resident on one amino acid, such as glutamic acid, is transferred onto the ketone group of another molecule as shown in the following example ... 

Table 1. IFABP-PX60-mediated transamination of a-ketoglutarate to glutamic acid in the presence of various hydrophobic amino acids...

GABA synthesis inhibitors act on the enzymes involved in the decarboxylation and transamination of GABA. Glutamic acid decarboxylase (GAD), the first enzyme in GABA biosynthesis, is inhibited easily by carbonyl reagents such as hydrazines [e.g., hydrazinopropionic acid (4.164) or isonicotinic acid hydrazide (4.165)], which trap pyridoxal, the essential cofactor of the enzyme. A more specific inhibitor is allylglycine (4.166). All of these compounds cause seizures and convulsions because they decrease the concentration of GABA. 

In the transamination reaction, in the presence of transaminase enzymes, (S)-glutamic acid reacts with the a-keto acid analog of the desired a-amino acid to give the desired (S)-amino acid and the keto analog of glutamic acid. 

Pyridoxal phosphate is the coenzyme for the enzymic processes of transamination, racemization and decarboxylation of amino-acids, and for several other processes, such as the dehydration of serine and the synthesis of tryptophan that involve amino-acids (Braunstein, 1960). Pyridoxal itself is one of the three active forms of vitamin B6 (Rosenberg, 1945), and its biochemistry was established by 1939, in considerable part by the work of A. E. Braunstein and coworkers in Moscow (Braunstein and Kritzmann, 1947a,b,c Konikova et al 1947). Further, the requirement for the coenzyme by many of the enzymes of amino-acid metabolism had been confirmed by 1945. In addition, at that time, E. E. Snell demonstrated a model reaction (1) for transamination between pyridoxal [1] and glutamic acid, work which certainly carried with it the implication of mechanism (Snell, 1945). 

An early step in the catabolism of amino acids is the separation of the amino group from the carbon skeleton. In most cases, the amino group is transferred to a-ketoglutarate to form glutamate. This transamination reaction requires the coenzyme pyridoxal phosphate. 

At pH 7.5 less than 1% of the compound exists in the open-chain a-keto-acid form while at pH 9 approximately 3% is in a form that reacts as a typical a-keto acid. Glutamine transaminase also catalyzes the transamination of glutamic acid y-A -methylamide the expected transamination product, a-keto-A-methylglutaramic acid has not yet been isolated from a transamination reaction mixture. However, this compound was... 

In addition to resolution approaches, there are three main methods to prepare amino acids by biological methods addition of ammonia to an unsaturated carboxylic acid the conversion of an a-keto acid to an amino acid by transamination from another amino acid, and the reductive animation of an a-keto acid. These approaches are discussed in Chapter 19 and will not be discussed here to avoid duplication. The use of a lyase to prepare L-aspartic acid is included in this chapter as is the use of decarboxylases to access D-glutamic acid. 

Products of Amino Acid Transamination Name and draw the structure of the a-keto acid resulting when each of the following amino acids undergoes transamination with a-ketoglutarate (a) aspartate, (b) glutamate, (c) alanine, (d) phenylalanine. 

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