POLYAMINES

POLYAMINES

1. Metabolism of Polyamines Gandham.Rajeev Email:[email protected]

2. The decarboxylation of amino acids or their derivatives results in formation of amines. Biogenic amines Amino acid Amine Decarboxylase, PLP CO2

3. Polyamines possess multiple amino groups. Putrescine , spermine & spermidine are biologically important polyamines. Spermine & spermidine were detected in human semen. Polyamines

4. Ornithine & S- adenosylmethionine are the precursors for polyamine synthesis. The four carbon moiety of SAM (not the methyl group) involved in polyamine formation. Ornithine decarboxylase acts on ornithine to split off CO2 & produce putrescine . Biosynthesis

5. Ornithine decarboxylase has short half life (10 minutes). It is a regulatory enzyme in polyamine synthesis. Its activity is increased by corticosteroids, testosterone & GH. Putrescine is converted to spermidine & spermine with the involvement of SAM.

6. SAM is decarboxylated to give decarboxylated SAM. SAM decarboxylase is a rare example, does not require PLP as coenzyme. The propylamino group of decarboxylated SAM is transferred to putrescine to give spermidine .

7. Synthesis of spermine requires one more molecule of decarboxylated SAM & this reaction is catalyzed by spermine synthase.

8. Degradation of polyamines The enzyme polyamine oxidase (liver peroxisomes) oxidizes spermine to spermidine & then to putrescine .

9. Spermidine & putrescine are excreted in urine in a conjugated form, as acetylated derivatives. Some amount of putrescine is also oxidized to NH3 & CO2.

10. Polyamines are basic in nature & possess multiple positive charges. They are associated with nucleic acids (DNA & RNA). They are involved in the synthesis of DNA, RNA & proteins. Functions of polyamines

11. References Textbook of Biochemistry – U Satyanarayana Textbook of Biochemistry – DM Vasudevan

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