title: Adenosine analogues as inhibitors of Trypanosoma brucei phosphoglycerate kinase: elucidation of a novel binding mode for a 2-amino-N(6)-substituted adenosine.
abstract: As part of a project aimed at structure-based design of adenosine analogues as drugs against African trypanosomiasis, N(6)-, 2-amino-N(6)-, and N(2)-substituted adenosine analogues were synthesized and tested to establish structure-activity relationships for inhibiting Trypanosoma brucei glycosomal phosphoglycerate kinase (PGK), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and glycerol-3-phosphate dehydrogenase (GPDH). Evaluation of X-ray structures of parasite PGK, GAPDH, and GPDH complexed with their adenosyl-bearing substrates led us to generate a series of adenosine analogues which would target all three enzymes simultaneously. There was a modest preference by PGK for N(6)-substituted analogues bearing the 2-amino group. The best compound in this series, 2-amino-N(6)- [2''(p-hydroxyphenyl)ethyl]adenosine (46b), displayed a 23-fold improvement over adenosine with an IC(50) of 130 microM. 2-[[2''-(p-Hydroxyphenyl)ethyl]amino]adenosine (46c) was a weak inhibitor of T. brucei PGK with an IC(50) of 500 microM. To explore the potential of an additive effect that having the N(6) and N(2) substitutions in one molecule might provide, the best ligands from the two series were incorporated into N(6),N(2)-disubstituted adenosine analogues to yield N(6)-(2''-phenylethyl)-2-[(2'' -phenylethyl)amino]adenosine (69) as a 30 microM inhibitor of T. brucei PGK which is 100-fold more potent than the adenosine template. In contrast, these series gave no compounds that inhibited parasitic GAPDH or GPDH more than 10-20% when tested at 1.0 mM. A 3.0 A X-ray structure of a T. brucei PGK/46b complex revealed a binding mode in which the nucleoside analogue was flipped and the ribosyl moiety adopted a syn conformation as compared with the previously determined binding mode of ADP. Molecular docking experiments using QXP and SAS program suites reproduced this "flipped and rotated" binding mode.
authors.affiliation: Department of Chemistry, University of Washington, Seattle, 98195, USA.
authors.forename: J C
authors.initials: JC
authors.lastname: Bressi
authors.forename: J
authors.initials: J
authors.lastname: Choe
authors.forename: M T
authors.initials: MT
authors.lastname: Hough
authors.forename: F S
authors.initials: FS
authors.lastname: Buckner
authors.forename: W C
authors.initials: WC
authors.lastname: Van Voorhis
authors.forename: C L
authors.initials: CL
authors.lastname: Verlinde
authors.forename: W G
authors.initials: WG
authors.lastname: Hol
authors.forename: M H
authors.initials: MH
authors.lastname: Gelb
mesh_terms: D000241:Adenosine / Q000031:analogs & derivatives* / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D000818:Animals; D020650:Combinatorial Chemistry Techniques; D018360:Crystallography, X-Ray; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000737:chemistry; D005993:Glycerolphosphate Dehydrogenase / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D010735:Phosphoglycerate Kinase / Q000037:antagonists & inhibitors / Q000737:chemistry*; D011485:Protein Binding; D013329:Structure-Activity Relationship; D014344:Trypanocidal Agents / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D014346:Trypanosoma brucei brucei / Q000737:chemistry* / Q000187:drug effects; D014349:Trypanosoma cruzi / Q000187:drug effects
chemical_list: C416350:2-amino-N(6)-(2''-(4-hydroxyphenyl)ethyl)adenosine; D004791:Enzyme Inhibitors; C416351:N(6)-(2''-phenylethyl)-2-((2'-phenylethyl)amino)adenosine; D014344:Trypanocidal Agents; D005993:Glycerolphosphate Dehydrogenase; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D010735:Phosphoglycerate Kinase; D000241:Adenosine