Structural analogues of reactive intermediates as inhibitors of glucosamine-6-phosphate synthase and phosphoglucose isomerase.
The active centers of phosphoglucose isomerase (PGI) and the hexose phosphate isomerase domain (HPI) of glucosamine-6-P (GlcN-6-P) synthase demonstrate apparent similarity in spatial arrangement of critical amino acid residues, except Arg272 of the former and Lys603 and Lys485 of the latter. Ten derivatives of d-hexitol-6-P, 5-phosphoarabinoate, or 6-phosphogluconate, structural analogues of putative cis-enolamine or cis-enolate intermediates, were tested as inhibitors of fungal GlcN-6-P synthase and PGI. None of the investigated compounds demonstrated equally high inhibitory potential against both enzymes. 2-Amino-2-deoxy-D-mannitol 6-P was found to be the strongest GlcN-6-P synthase inhibitor in the series, with an inhibition constant equal to 9.0 (+/-1.0) x 10(-6)M. On the contrary, 5-phosphoarabinoate (5PA) exhibited specificity for PGI, with K(i)=2.2 (+/-0.1) x 10(-6) M. N-acetylation substantially lowered the GlcN-6-P synthase inhibitory potential of 2-amino-2-deoxy-D-glucitol-6-P but strongly enhanced inhibitory potential of this compound towards PGI. Molecular modeling studies revealed that interactions of the C1-C2 part of transition state analogue inhibitors with the respective areas demonstrating different distribution of molecular electrostatic potential (MEP) inside HPI and PGI active centers determined enzyme:ligand affinity. In Escherichia coli HPI, a patch of the negative potential created by Glu488 aided by Val399, supposed to stabilize a putative positively charged intermediate, especially attracts ligands containing 2-amino function. The Arg272, Lys210, and Gly271 peptide bond nitrogen system, present in the corresponding space of rabbit PGI, creates an area of positive MEP, stabilizing cis-enolate intermediate and attracting its structural mimics, such as 5PA.
Milewski
Sławomir
S
Department of Pharmaceutical Technology and Biochemistry, Gdańsk University of Technology, 11/12 Narutowicza St., 80-952 Gdańsk, Poland. milewski@chem.pg.gda.pl
Janiak
Agnieszka
A
Wojciechowski
Marek
M
D000596:Amino Acids / Q000737:chemistry; D000818:Animals; D001665:Binding Sites; D020134:Catalytic Domain; D004791:Enzyme Inhibitors / Q000737:chemistry*; D004926:Escherichia coli / Q000201:enzymology*; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors*; D005956:Glucose-6-Phosphate Isomerase / Q000037:antagonists & inhibitors*; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing) / Q000037:antagonists & inhibitors*; D007700:Kinetics; D008958:Models, Molecular; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011817:Rabbits; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship
D000596:Amino Acids; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D005945:Glutamine-Fructose-6-Phosphate Transaminase (Isomerizing); D005956:Glucose-6-Phosphate Isomerase