scholarly journals Glucosamine-6-phosphate synthase from Escherichia coli: mechanism of the reaction at the fructose 6-phosphate binding site

1989 ◽  
Vol 111 (8) ◽  
pp. 3029-3034 ◽  
Author(s):  
Beatrice Golinelli-Pimpaneau ◽  
Francois Le Goffic ◽  
Bernard Badet
Keyword(s):  
Escherichia Coli ◽  
Binding Site ◽  
Phosphate Binding ◽  
Mechanism Of The Reaction ◽  
Phosphate Synthase

scholarly journals Structure of l-Xylulose-5-Phosphate 3-Epimerase (UlaE) from the Anaerobic l-Ascorbate Utilization Pathway of Escherichia coli: Identification of a Novel Phosphate Binding Motif within a TIM Barrel Fold

2008 ◽  
Vol 190 (24) ◽  
pp. 8137-8144 ◽  
Author(s):  
Rong Shi ◽  
Marco Pineda ◽  
Eunice Ajamian ◽  
Qizhi Cui ◽  
Allan Matte ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Binding Site ◽  
Active Site ◽  
Active Sites ◽  
Triosephosphate Isomerase ◽  
Pentose Phosphate ◽  
Binding Motif ◽  
Phosphate Binding ◽  
Activity Measurements ◽  
Tim Barrel

ABSTRACT Three catabolic enzymes, UlaD, UlaE, and UlaF, are involved in a pathway leading to fermentation of l-ascorbate under anaerobic conditions. UlaD catalyzes a β-keto acid decarboxylation reaction to produce l-xylulose-5-phosphate, which undergoes successive epimerization reactions with UlaE (l-xylulose-5-phosphate 3-epimerase) and UlaF (l-ribulose-5-phosphate 4-epimerase), yielding d-xylulose-5-phosphate, an intermediate in the pentose phosphate pathway. We describe here crystallographic studies of UlaE from Escherichia coli O157:H7 that complete the structural characterization of this pathway. UlaE has a triosephosphate isomerase (TIM) barrel fold and forms dimers. The active site is located at the C-terminal ends of the parallel β-strands. The enzyme binds Zn2+, which is coordinated by Glu155, Asp185, His211, and Glu251. We identified a phosphate-binding site formed by residues from the β1/α1 loop and α3′ helix in the N-terminal region. This site differs from the well-characterized phosphate-binding motif found in several TIM barrel superfamilies that is located at strands β7 and β8. The intrinsic flexibility of the active site region is reflected by two different conformations of loops forming part of the substrate-binding site. Based on computational docking of the l-xylulose 5-phosphate substrate to UlaE and structural similarities of the active site of this enzyme to the active sites of other epimerases, a metal-dependent epimerization mechanism for UlaE is proposed, and Glu155 and Glu251 are implicated as catalytic residues. Mutation and activity measurements for structurally equivalent residues in related epimerases supported this mechanistic proposal.

Biodegradative ornithine decarboxylase of Escherichia coli. Purification, properties, and pyridoxal 5'-phosphate binding site

Biochemistry ◽  
1975 ◽  
Vol 14 (16) ◽  
pp. 3675-3681 ◽  
Author(s):  
Deborah Applebaum ◽  
Donna L. Sabo ◽  
Edmond H. Fischer ◽  
David R. Morris
Keyword(s):  
Escherichia Coli ◽  
Binding Site ◽  
Ornithine Decarboxylase ◽  
Phosphate Binding

scholarly journals The binding of substrates and modifiers to glucosamine synthetase

1971 ◽  
Vol 121 (4) ◽  
pp. 721-730 ◽  
Author(s):  
P. J. Winterburn ◽  
C. F. Phelps
Keyword(s):  
Binding Site ◽  
Binding Sites ◽  
Catalytic Site ◽  
Phosphate Binding ◽  
Inhibitor Binding ◽  
Nucleotide Sugar ◽  
Chemical Denaturation ◽  
Feedback Inhibitor ◽  
Denaturation Rate ◽  
Mechanism Of The Reaction

1. The binding of substrates and effectors to glucosamine synthetase (l-glutamine–d-fructose 6-phosphate aminotransferase, EC 2.6.1.16) was studied by using the ligand to alter the denaturation rate of the enzyme. The free enzyme bound fructose 6-phosphate, glucose 6-phosphate and UDP-N-acetylglucosamine, but not glutamine, AMP or UTP. Glucose 6-phosphate and AMP increased the binding of UDP-N-acetylglucosamine whereas UTP decreased the interaction between the enzyme and the feedback inhibitor. UDP-N-acetylglucosamine induced a glutamine-binding site on the enzyme. 2. Selective thermal or chemical denaturation revealed that the UDP-N-acetylglucosamine-binding site was not located at the catalytic site. The UTP site could not be distinguished from that for the nucleotide sugar. The AMP- and glucose 6-phosphate-binding sites were distinct from the catalytic and feedback-inhibitor-binding sites. 3. The specificity of the glutamine-binding site was investigated by using a series of potential analogues. 4. A model is proposed for the action of the effectors and the mechanism of the reaction discussed in kinetic and chemical terms.

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