TRANSDEAMINATION AND DEAMINATION

By:Minhaz AhmedBBI11014Int msc V semTezpur universityAssam

CONTENT

• TRANSDEAMINATION• TRANSAMINATION• DEAMINATION

TRANSDEAMINATIONThe amino group of amino acids is released by a coupled reaction, TRANSDEAMINATION Transamination followed by oxidative deamination.Transamination takes place in the cytoplasm of all the cells of the body : the amino group is transported to liver as glutamic acid, which is finally oxidatively deaminated in the mitochondria of hepatocytes.Thus, the two components of the reaction are physically far away, but phisiologically they are coupled. Hence, Transdeamination.

• Transamination is a chemical reaction between two molecules.

• One is an amino acid, which contains an amine (NH2) group.

• The other is a keto acid, which contains a keto (=O) group.

• In transamination, the NH2 group on one molecule is exchanged with the =O group on the other molecule. The amino acid becomes a keto acid, and the keto acid becomes an amino acid.

• Transamination in biochemistry is accomplished by enzymes called transaminases or aminotransferases.

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Transamination transfer of -NH2 group from one substrate to other

• most AA (not Lys, Thr, Pro, His, Trp, Arg, Met)

• amino group is transferred from AA to 2-oxoglutarate

• cofactor – pyridoxal phosphate ( Schiff bases)

• reversible reaction important for synthesis of AA

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General scheme of transamination

CH2CH2COOH

O

CHOOC+R CH

NH2

COOH

aminokyselina 2-oxoglutarát

HOOC CH CH2CH2COOH

NH2

+R C

O

COOH

glutamát2-oxokyselina

aminotransferasapyridoxalfosfát

amino acid

2-oxo acid

2-oxoglutarate

glutamate

aminotransferase

pyridoxal phosphate

DEAMINATION

• Deamination is the removal of an amine group from a molecule. Enzymes which catalyse this reaction are called deaminases.

• In the human body, deamination takes place primarily in the liver, however glutamate is also deaminated in the kidneys.

• Deamination is the process by which amino acids are broken down if there is an excess of protein intake. The amino group is removed from the amino acid and converted to ammonia.

Deamination of amino acids

•Deamination - elimination of amino group from amino acid with ammonia formation.

• Four types of deamination: • - oxidative (the most important for

higher animals), • - reduction, • - hydrolytic, and • - intramolecular

Reduction deamination:

R-CH(NH2)-COOH + 2H+ R-CH2-COOH + NH3

amino acid fatty acid

Hydrolytic deamination:

R-CH(NH2)-COOH + H2O R-CH(OH)-COOH + NH3

amino acid hydroxyacid

Intramolecular deamination:

R-CH(NH2)-COOH R-CH-CH-COOH + NH3

amino acid unsaturated fatty acid

During oxidative deamination, an amino acid is converted into the corresponding keto acid by the removal of the amine functional group as ammonia.

The amine functional group is replaced by the ketone group. The ammonia eventually goes into the urea cycle.

Oxidative deamination occurs primarily on glutamic acid because glutamic acid was the end product of many transamination reactions.

The glutamate dehydrogenase is controlled by ATP and ADP. ATP acts as an inhibitor whereas ADP is an activator.

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Proteins

NH3

glutamate

glutamate + urea

(excretion by urine)

2-oxoglutarate +

glutamine

proteolysis

dehydrogenation + deamination

detoxication in liver deamidation

in kidney

amino acids

transamination

detoxication in other tissues

NH4+

(excretion by urine)

NH4+

(excretion by urine)

deamination in kidney

Intake, catabolism, and excretion of nitrogen

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