Metabolism of Ammonia Dr. Rohini C Sane

Metabolism of AmmoniaNH3 → NH4 ⁺ ion ( exist ammonium ion at p H 7.4)

I .Formation of Ammonia :

a ) Transamination & Deamination of biogenic amines ,NH2 group of Purines & Pyrimidine

b) Urea bacterial urease NH3

II . Transport & storage :

Conc of serum ammonia 10 -20 micro gram /dl

Efficient transport &immediate utilization of ammonia for urea synthesis

Ammonia is transported as Glutamine & Alanine (Glucose –Alanine cycle

No free Ammonia in serum under physiological conditions

Functions of AmmoniaWaste products of nitrogen

Synthesis of compounds like

a) Non essential amino acids

b) Purines

c) Pyrimidine

d) Amino sugars

e) Asparagine

f) NH₄⁺(acid base balance )

PURINE BASE

Disposal of Ammonia1) Ammonitelic : ammonia excreted in water eg aquatic animals

2) Uricotelic : ammonia excreted as uric acid eg reptiles & birds

3) Ureotelic : ammonia excreted as urea (non toxic ,water soluble )eg mammals

AMMONIA URIC ACID

UREA

Toxicity of Ammonia

Symptoms of Toxicity of Ammonia

• Marginal elevation –toxic to brain

• Slurring of speech

• Blurring of vision

• Tremors

• Coma

• Death

Biochemistry of Toxicity of AmmoniaNH3 ↑

↓GLUTAMATE ↑

↓α KGA (intermediate of TCA CYCLE ) ↓

↓TCA ( impairment of TCA ) ↓

↓ATP in brain ↓

Hyperammonemia

(a) Genetic defects in enzymes of Urea cycle (neonates )

↓

Mental retardation

(b) Acquired Hepatitis ( alcoholism- defective urea synthesis )

Metabolic disorders of Urea cycleType of Hyperammonemmia Defective Enzyme

HYPER AMMONEMMIA I CPS I

HYPER AMMONEMMIA II Ornithine Trans carbomylase

HYPER AMMONEMMIA IIICitullinemia

Argino sucdefective encinatesynthtase

HYPER AMMONEMMIA IVArginosuccinic aciduria

Arginosuccinase

HYPER AMMONEMMIA VHyperargininemia

Arginase