Title
Mechanism of Action of Escherichia coli Phosphoribosylaminoimidazolesuccinocarboxamide Synthetase
Campus Units
Biochemistry, Biophysics and Molecular Biology
Document Type
Article
Publication Version
Published Version
Publication Date
1-2005
Journal or Book Title
Biochemistry
Volume
44
Issue
2
First Page
766
Last Page
774
DOI
10.1021/bi048191w
Abstract
The conversion of ATP, l-aspartate, and 5-aminoimidazole-4-carboxyribonucleotide (CAIR) to 5-aminoimidazole-4-(N-succinylcarboxamide) ribonucleotide (SAICAR), ADP, and phosphate by phosphoribosylaminoimidazolesuccinocarboxamide synthetase (SAICAR synthetase) represents the eighth step of de novo purine nucleotide biosynthesis. SAICAR synthetase and other enzymes of purine biosynthesis are targets of natural products that impair cell growth. Prior to this study, no kinetic mechanism was known for any SAICAR synthetase. Here, a rapid equilibrium random ter-ter kinetic mechanism is established for the synthetase from Escherichia coli by initial velocity kinetics and patterns of linear inhibition by IMP, adenosine 5‘-(β,γ-imido)triphosphate (AMP-PNP), and maleate. Substrates exhibit mutual binding antagonism, with the strongest antagonism between CAIR and either ATP or l-aspartate. CAIR binds to the free enzyme up to 200-fold more tightly than to the ternary enzyme−ATP−aspartate complex, but the latter complex may be the dominant form of SAICAR synthetase in vivo. IMP is a competitive inhibitor with respect to CAIR, suggesting the possibility of a hydrogen bond interaction between the 4-carboxyl and 5-amino groups of enzyme-bound CAIR. Of several aspartate analogues tested (hadacidin, l-malate, succinate, fumarate, and maleate), maleate was by far the best inhibitor, competitive with respect to l-aspartate. Inhibition by IMP and maleate is consistent with a chemical mechanism for SAICAR synthetase that parallels that of adenylosuccinate synthetase.
Copyright Owner
American Chemical Society
Copyright Date
2005
Language
en
File Format
application/pdf
Recommended Citation
Nelson, Scott W.; Binkowski, Daniel Joseph; Honzatko, Richard B.; and Fromm, Herbert J., "Mechanism of Action of Escherichia coli Phosphoribosylaminoimidazolesuccinocarboxamide Synthetase" (2005). Biochemistry, Biophysics and Molecular Biology Publications. 78.
https://lib.dr.iastate.edu/bbmb_ag_pubs/78
Comments
Reprinted (adapted) with permission from Biochemistry 44 (2005): 766, doi: 10.1021/bi048191w. Copyright 2005 American Chemical Society.