POLYAMINES

2.  The decarboxylation of amino acids or their
derivatives results in formation of 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.

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.

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.

10.  The enzyme polyamine oxidase (liver
peroxisomes) oxidizes spermine to
spermidine & then to putrescine.

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

12.  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.

13.  Textbook of Biochemistry – U Satyanarayana
 Textbook of Biochemistry – DM Vasudevan