PROTEIN METABOLISM

DR. MD. MAHBUBUR RAHMAN

MBBS, M. Phil, MSc. (Biotechnology)

ASSISTANT PROFESSOR

DEPT. OF BIOCHEMISTRY

RAJSHAHI MEDICAL COLLEGE

After the end of the session student will able to know the

Transamination and Deamination of protein (Transaminase enzyme)

Source of Ammonia and disposal of ammonia

Ammonia intoxication

Urea cycle

Removal of nitrogen from amino acid

Transamination by Transaminase enzyme

Alanine aminotransferase (ALT)

Aspertate aminotransferase ( AST)

Oxidative Deamination By

Glutamate dehydrogenase

Definition of Transamination

Transamination: Transfer of an amino group of an amino acid to keto acid is known is transamination.

α -ketoglutarate Pyruvate

Alanine Glutamate

Transaminase enzyme

Alanine Aminotransferase (ALT)

Aspartate Aminotransferase (AST)

Diagnostic value of Aminotransferase

Liver disease

Non hepatic disease – MI, Muscle disorder, Bone disorder

Definition of Deamination

Deamination: Removal of an amino group from an amino acid is known as deamination.

Glutamate dehydrogenase : the oxidative deamination of amino acid.

Source of ammonia

From amino acid

From Glutamine By glutaminase in the kidney

From bacterial action in the intestine

From amines that are obtained from diet and

From purines and pyrimidines

Transport of ammonia in the circulation

Urea: Formation in the liver then transported to kidney where it passes into the glomerular filtrate.

Glutamine : is synthesize by glutamine synthetase enzyme – that occurs in the brain.

Hyperammonemia

Serum ammonia level 5-50 µmol /L.

Hyperammonemia has direct toxic effect on the CNS.

Elevated ammonia causes the symptom of ammonia intoxication

Slurring of speech , Somnolence, Vomiting cerebral edema, Blurring of vision ultimatly comma and death.

UREA CYCLE

Organ : Liver

Site : Mitochondria and cytosol

Substrate : Ammonia & CO2

Product : Urea

Aspartate +NH3 + 3ATP Urea+ Fumerate + 2 ADP + AMP +2Pi + PPi +3 H2O

UREA CYCLE

Reaction of Urea cycle

Formation of Carbamoyl phosphate by CPS-I

Formation of Citrulin

Synthesis of Argininosuccinate

Cleavage of Arginionosuccinate

Cleavage of Arginin to urea and ornithin

Fate of Urea

Urea diffuses from liver and transported to the kidney where it is filtered and excreted in the urine.