Amino Acids that form α-ketoglutarate via Glutamate

1. Glutamine: This amino acid is hydrolyzed to glutamate and ammonia by the enzyme glutaminase. Glutamate is converted to α-ketoglutarate by transamination or through oxidative deamination by glutamate dehydrogenase.

2. Proline: This amino acid is oxidized to glutamate. Glutamate is transaminated or oxidatively deaminated to form α-ketoglutarate.

3. Arginine: This amino acid is hydrolyzed by arginase to produce ornithine (and urea). [Note: The reaction occurs primarily in the liver as part of the urea cycle.] Ornithine is subsequently converted to α-ketoglutarate, with glutamate semialdehyde as an intermediate.

4. Histidine: This amino acid is oxidatively deaminated by histidase to urocanic acid, which subsequently forms N-formiminoglutamate  ([FIGlu], Fig. 1). FIGlu donates its formimino group to tetrahydrofolate (THF), leaving glutamate, which is degraded as described above. [Note: Individuals deficient in folic acid excrete increased amounts of FIGlu in the urine, particularly after ingestion of a large dose of histidine. The FIGlu excretion test has been used in diagnosing a deficiency of folic acid.

Figure 1: Degradation of histidine. NH₃ = ammonia.

مواضيع ذات صلة

آلية عمل المجموعة الأولى من الهرمونات

الهرمونات وآليات الاستتباب

تدرك (تقويض) الهرمونات وتعطيلها

نقل الهرمونات في البلازما

تغاير خزن الهرمونات وإفرازها

تخليق POMC ومعالجته

The Amino Acids

Absorption & Transport of Transition Metals

Physiologic Roles of The Essential Transition Metals

تخليق الأنجيوتنسين

تخلیق PTH

تخليق الأنسولين