title: Binding and inhibition of human spermidine synthase by decarboxylated S-adenosylhomocysteine.
abstract: Aminopropyltransferases are essential enzymes that form polyamines in eukaryotic and most prokaryotic cells. Spermidine synthase (SpdS) is one of the most well-studied enzymes in this biosynthetic pathway. The enzyme uses decarboxylated S-adenosylmethionine and a short-chain polyamine (putrescine) to make a medium-chain polyamine (spermidine) and 5'-deoxy-5'-methylthioadenosine as a byproduct. Here, we report a new spermidine synthase inhibitor, decarboxylated S-adenosylhomocysteine (dcSAH). The inhibitor was synthesized, and dose-dependent inhibition of human, Thermatoga maritima, and Plasmodium falciparum spermidine synthases, as well as functionally homologous human spermine synthase, was determined. The human SpdS/dcSAH complex structure was determined by X-ray crystallography at 2.0 Å resolution and showed consistent active site positioning and coordination with previously known structures. Isothermal calorimetry binding assays confirmed inhibitor binding to human SpdS with K(d)  of 1.1 ± 0.3 μM in the absence of putrescine and 3.2 ± 0.1 μM in the presence of putrescine. These results indicate a potential for further inhibitor development based on the dcSAH scaffold.
authors: Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, USA.
authors: Jolita
authors: J
authors: Sečkutė
authors: Diane E
authors: DE
authors: McCloskey
authors: H Jeanette
authors: HJ
authors: Thomas
authors: John A
authors: JA
authors: Secrist
authors: Anthony E
authors: AE
authors: Pegg
authors: Steven E
authors: SE
authors: Ealick
mesh_terms: D001665:Binding Sites; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D003653:Decarboxylation; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D010963:Plasmodium falciparum / Q000201:enzymology; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011700:Putrescine / Q000378:metabolism; D012435:S-Adenosylhomocysteine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D013095:Spermidine / Q000096:biosynthesis* / Q000378:metabolism; D011436:Spermidine Synthase / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism*; D020124:Thermotoga maritima / Q000201:enzymology
chemical_list: D004791:Enzyme Inhibitors; C012703:S-adenosyl-3-thiopropylamine; D012435:S-Adenosylhomocysteine; D011436:Spermidine Synthase; D013095:Spermidine; D011700:Putrescine