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Fig. 1 | Cancer Cell International

Fig. 1

From: Polyamines and related signaling pathways in cancer

Fig. 1

(5) PTS (adapted from [18]): there are several different theories for the polyamine transport system: a Spermine combines with the heparan sulfate group in GPC1 on the cell surface and enters into the cell. b Polyamine transport is mediated by endocytosis and solute carrier transport mechanisms. c Polyamine is transported into the cell by a currently unknown transporter driven by membrane potential.

Polyamine biosynthesis and metabolic transport pathways. (1) Polyamine synthesis: arginine is converted into ornithine and agmatine, which is then catalyzed and decomposed into putrescine and urea by ornithine decarboxylase (ODC) and agmatine (AGMAT). Next, putrescine is converted to spermidine and spermine. (2) Methionine salvage: S-adenosylmethionine (dcAdoMet) decarboxylation provides aminopropyl for the formation of spermidine and spermine, and its product 5′-methylthioadenosine (MTA) is recovered to methionine through a series of enzymatic reactions. Subsequently, methionine is catalyzed by methionine adenosine transferase 2 (MAT2) and S-adenosylmethionine decarboxylase (AdoMetDC) to generate dcAdoMet. (3) ODC-AZ axis: the activity of ornithine decarboxylase is regulated by antizyme (AZ) and antizyme inhibitor (AZI). (4) Polyamine catabolism: spermidine and spermine are decomposed by spermidine/sperm-N-acetyltransferase (SSAT) to produce N-acetylspermidine and N-acetylspermine, respectively.

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