-Ketoglutarate (AKG)

-Ketoglutarate is a citric acid cycle intermediate and an important compound in amino acid metabolism and transamination reactions. Some relevant metabolic reactions involving AKG are shown below.

-Ketoglutarate is also involved in the malate/aspartate shuttle (see here) of mitochondria (Figure 15.11) and enzymatic reactions catalyzed by procollagen proline hydroxylase that hydroxylate procollagen proline residues in collagen synthesis (Figure 21.4).

Reactions:

1. Isocitrate + NAD+ <=> -Ketoglutarate + CO 2 + NADH (catalyzed by Isocitrate Dehydrogenase)

2. -Ketoglutarate + NAD+ + CoASH <=> Succinyl-CoA + CO 2 + NADH (catalyzed by Ketoglutarate Dehydrogenase Complex)

3. Oxaloacetate + Glutamate <-> Aspartate + -Ketoglutarate (transamination catalyzed by SGOT).

4. -Ketoglutarate + Glutamine + NADPH + H+ <=> 2 Glutamate + NADP+ (Catalyzed by Glutamate Synthase)

5. Alanine + -Ketoglutarate <=> Pyruvate + Glutamate (catalyzed by Aminotransferase).

6. Glutamate + Pyruvate <=> -Ketoglutarate + Alanine (catalyzed by SGPT)

See also: Enzymes of the citric acid cycle, Figure 14.3, Table 14.1, Citric Acid Cycle Intermediates in Amino Acid Metabolism, Glutamate as a Precursor of Other Amino Acids, Transamination in Amino Acid Metabolism

INTERNET LINKS:

> 1. Citric Acid Cycle

> 2. Urea Cycle and Metabolism of Amino Groups