transamination.pptx

For Nursing Students

1. Biochemistry for PBBN Transamination & Deaminationa BRAINSTROMING NOTES TO PRINT

2. Definition The transfer ofan amino (-NH2) group from an amino acid to a keto acid is known as transamination . One among the major degradation pathway to convert essential aminoacids to nonessential aminoacids .

3. Transamination Accomplished by enzymes called transaminases or aminotransferases . α- ketoglutarate acts as a major amino group acceptor and produces glutamate as the new amino acid. Amino acid + α- ketoglutarate ↔ α- keto acid + Glutamate

4. Transamination Glutamate's amino group, in turn, is transferred to oxaloacetate in a second transamination reaction yielding aspartate . Glutamate + oxaloacetate ↔ α- ketoglutarate + aspartate

5. Salient Feature of Transamination All transaminases requires Pyridoxal phosphate (PLP), a coenzyme derived from vitamin B6. Specific transaminases exist for each pair of amino and keto acids. However, only two- namely, aspartate transaminase and alanine transaminase - make a significant contribution for transamination . There is no free NH3 liberated, only the transfer of amino group occurs.

6. Salient Feature of Transamination Transamination is reversible. Transamination is very important for the redistribution of amino groups and production of non- essensial amino acid. Transamination diverts the excess amino acids towards energy generation. The amino acids undergo transamination to finally concentrate nitrogen in glutamate. All amino acids except lysine, threonine , proline , and hydroxyproline participate in transamination . Transamination is not restricted to alfa -amino group only. Delta-amino group of ornithine is transaminated . Serum transaminases are important for diagnostic and prognostic purpose.

7. Mechanism of Transamination Transamination occurs in two stages: Transfer of the amino group to the coenzyme pyrodixal phosphate to form pyridoxamine phosphate. The amino group of pyridoxamine phosphate is then transferred to a ketoacid to produce a new amino acid and the enzyme with PLP is regenerated.

8. Transamination (Stage A)

9. Transamination (Stage B)

10. Deamination The removal of amino group from the amino acisaas NH3 is deamination . Deamination result in the liberation of amonia for urea synthesis. Deamination may be either oxidative of non-oxidative.

11. Deaminataion (Oxidative) Liberation of Free Amonnia from the amino group of amino acids coupled with oxidation. Takes place in kidney and liver. Provide NH3 for Urea synthesis and Alfa- keto acids for variety of reactions.

12. Oxidative deamination Role of glutamate dehydrogenase : Amino acids are transferred to alfa-keto glutarate to produce glutamate. Glutamate catalysed by glutamate dehydrogenase (GDH) to liberate ammonia. Conversion of glutamate to alfa-ketoglutarate occurs through the formation of an itermediate , alfa-iminoglutarate .

13. Oxidative deamination Oxidativedeamination by amino acid oxidases : L-Amino acidoxidase and D-amino acid Oxide are flavoproteins , prossessing FMN ( Flavin Mononucleotide) and FAD ( Flavin Adenin Dinucleotide ) respectively. They act on the corresponding amino acids (L or D) to produce alfa-keto acids and NH3.

14. Non-Oxidative Deamination The amino acids can be deaminated to liberate NH3 without undergoing oxidation. A) Amino acid dehydrases : Serine, Threonine and Homoserine are the hydroxy amino acids. They undergo non-oxidative deaminations catalysed by PLP-dependent dehydrases . B) Amino Acid Desulfhydrases : The sulfur amino acids, namely Cysteine and Homocysteine , undergo deamination coupled with desulfhydration to give keto acids.

15. Non-Oxidative Deamination B) Amino Acid Desulfhydrases : The sulfur amino acids, namely Cysteine and Homocysteine , undergo deamination coupled with desulfhydration to give keto acids.

16. Non-Oxidative Deamination C) Deamination of Histidine : The enzyme histidine acts on histidine to liberate NH3 by a non-oxidative deamination process.