Publications

• Biosynthesis of the purines. XXIV. The enzymatic synthesis of 5-amino-1-ribosyl-4-imidazolecarboxylic acid 5'-phosphate from 5-amino-1-ribosylimidazole 5'-phosphate and carbon dioxide.

  LUKENS L.N., BUCHANAN J.M.

  J Biol Chem 234:1799-1805(1959) [PubMed] [EuropePMC]

• Mechanism of action of Escherichia coli phosphoribosylaminoimidazolesuccinocarboxamide synthetase.

  Nelson S.W., Binkowski D.J., Honzatko R.B., Fromm H.J.

  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 p ... >> More

  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'-(beta,gamma-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. << Less

  Biochemistry 44:766-774(2005) [PubMed] [EuropePMC]

• Cloning and characterization of a 12-gene cluster from Bacillus subtilis encoding nine enzymes for de novo purine nucleotide synthesis.

  Ebbole D.J., Zalkin H.

  An approximately 16-kilobase pair region of the Bacillus subtilis chromosome at 55 degrees containing genes for de novo purine nucleotide synthesis (Piggot, P. J., and Hoch, J. A. (1985) Microbiol. Rev. 49, 158-179) was cloned. The nucleotide sequence of over 13 kilobase pairs indicates that this ... >> More

  An approximately 16-kilobase pair region of the Bacillus subtilis chromosome at 55 degrees containing genes for de novo purine nucleotide synthesis (Piggot, P. J., and Hoch, J. A. (1985) Microbiol. Rev. 49, 158-179) was cloned. The nucleotide sequence of over 13 kilobase pairs indicates that this region contains a cluster of 12 genes, 11 of which encode enzymes that catalyze the 10 reactions for de novo purine nucleotide synthesis from 5-phosphoribosyl 1-pyrophosphate to IMP. The genes were identified by complementation of Escherichia coli pur mutants and by sequence comparisons with homologous enzymes. The cluster is likely an operon and is organized into three groups of overlapping genes followed by the last gene: purEKB-purC(orf)QLF-purMNH(J)-purD. Sequence comparisons provide evidence for homology of monofunctional purine nucleotide biosynthetic enzymes from B. subtilis with the corresponding multifunctional enzymes from yeast and Drosophila. Sequence alignment of the phosphoribosylaminoimidazole carboxylase heterodimer from B. subtilis with the monomeric enzyme from Methanobrevibacter smithii indicates an evolutionary relationship between these two enzymes. S1 nuclease analysis was used to map the mRNA 5' and 3' ends and to estimate levels of mRNA. These experiments indicate that synthesis of purine nucleotides is regulated independently by adenine and guanine nucleotides. Adenine nucleotides regulate transcription initiation. Guanine nucleotides regulate transcription by a termination-antitermination mechanism in a 242-nucleotide 5' untranslated mRNA leader region. Groups of overlapping genes, regulated at least in part by transcription termination-antitermination is likely to be a common theme for genetic organization and regulation of biosynthetic genes in this Gram-positive organism. << Less

  J. Biol. Chem. 262:8274-8287(1987) [PubMed] [EuropePMC]

• Identification of the purC gene product of Escherichia coli.

  Parker J.

  The purC region of the Escherichia coli chromosome was isolated from in vivo-derived lambda transducing bacteriophages and cloned in high-copy-number plasmids. The product of the purC gene, phosphoribosylaminoimidazolesuccinocarboxamide synthetase, was identified as a protein with an Mr of ca. 27, ... >> More

  The purC region of the Escherichia coli chromosome was isolated from in vivo-derived lambda transducing bacteriophages and cloned in high-copy-number plasmids. The product of the purC gene, phosphoribosylaminoimidazolesuccinocarboxamide synthetase, was identified as a protein with an Mr of ca. 27,000. The level of the protein is increased by more than 60-fold in strains carrying the gene on a high-copy-number plasmid. Purine addition represses the enzyme level in both plasmid- and non-plasmid-containing strains. << Less

  J Bacteriol 157:712-717(1984) [PubMed] [EuropePMC]

• Cloning of a chicken liver cDNA encoding 5-aminoimidazole ribonucleotide carboxylase and 5-aminoimidazole-4-N-succinocarboxamide ribonucleotide synthetase by functional complementation of Escherichia coli pur mutants.

  Chen Z.D., Dixon J.E., Zalkin H.

  We have used functional complementation of Escherichia coli pur mutants to clone avian cDNA encoding 5-aminoimidazole ribonucleotide (AIR) carboxylase-5-aminoimidazole-4-N-succinocarboxamide ribonucleotide (SAICAR) synthetase, the bifunctional enzyme catalyzing steps 6 and 7 in the pathway for de ... >> More

  We have used functional complementation of Escherichia coli pur mutants to clone avian cDNA encoding 5-aminoimidazole ribonucleotide (AIR) carboxylase-5-aminoimidazole-4-N-succinocarboxamide ribonucleotide (SAICAR) synthetase, the bifunctional enzyme catalyzing steps 6 and 7 in the pathway for de novo purine nucleotide synthesis. Mutational analyses have been used to establish the structure-function relationship: NH2-SAICAR synthetase-AIR carboxylase-COOH. The amino acid sequence of the SAICAR synthetase domain is homologous to that of bacterial purC-encoded enzymes, and the sequence of the following AIR carboxylase domain is homologous to that of bacterial purE-encoded enzymes. In E. coli, AIR carboxylase is the product of genes purEK with the purK subunit postulated to have a role in CO2 binding. The avian enzyme lacks sequences corresponding to purK yet functions in E. coli. Functional complementation of E. coli pur mutants can be used to clone additional avian cDNAs for de novo purine nucleotide synthesis. << Less

  Proc. Natl. Acad. Sci. U.S.A. 87:3097-3101(1990) [PubMed] [EuropePMC]

• The Drosophila melanogaster ade5 gene encodes a bifunctional enzyme for two steps in the de novo purine synthesis pathway.

  O'Donnell A.F., Tiong S., Nash D., Clark D.V.

  Steps 6 and 7 of de novo purine synthesis are performed by 5-aminoimidazole ribonucleotide carboxylase (AIRc) and 4-[(N-succinylamino)carbonyl]-5-aminoimidazole ribonucleotide synthetase (SAICARs), respectively. In vertebrates, a single gene encodes AIRc-SAICARs with domains homologous to Escheric ... >> More

  Steps 6 and 7 of de novo purine synthesis are performed by 5-aminoimidazole ribonucleotide carboxylase (AIRc) and 4-[(N-succinylamino)carbonyl]-5-aminoimidazole ribonucleotide synthetase (SAICARs), respectively. In vertebrates, a single gene encodes AIRc-SAICARs with domains homologous to Escherichia coli PurE and PurC. We have isolated an AIRc-SAICARs cDNA from Drosophila melanogaster via functional complementation with an E. coli purC purine auxotroph. This cDNA encodes AIRc yet is unable to complement an E. coli purE mutant, suggesting functional differences between Drosophila and E. coli AIRc. In vertebrates, the AIRc-SAICARs gene shares a promoter region with the gene encoding phosphoribosylamidotransferase, which performs the first step in de novo purine synthesis. In Drosophila, the AIRc-SAICARs gene maps to section 11B4-14 of the X chromosome, while the phosphoribosylamidotransferase gene (Prat) maps to chromosome 3; thus, the close linkage of these two genes is not conserved in flies. Three EMS-induced X-linked adenine auxotrophic mutations, ade4(1), ade5(1), and ade5(2), were isolated. Two gamma-radiation-induced (ade5(3) and ade5(4)) and three hybrid dysgenesis-induced (ade5(5), ade5(6), and ade5(8)) alleles were also isolated. Characterization of the auxotrophy and the finding that the hybrid dysgenesis-induced mutations all harbor P transposon sequences within the AIRc-SAICARs gene show that ade5 encodes AIRc-SAICARs. << Less

  Genetics 154:1239-1253(2000) [PubMed] [EuropePMC]