Related Experiment Video
Updated: Jun 13, 2026
07:59
Spectrophotometric Methods for the Study of Eukaryotic Glycogen Metabolism
Published on: August 19, 2021
6-Phosphogluconate dehydrogenase mechanism: evidence for allosteric modulation by substrate.
Stefania Hanau1, Katy Montin, Carlo Cervellati
1Department of Biochemistry and Molecular Biology, University of Ferrara, 44100 Ferrara, Italy. hns@unife.it
The Journal of Biological Chemistry
|May 11, 2010
Summary
The study on 6-phosphogluconate dehydrogenase (6PGDH) reveals its mechanism in reductive carboxylation. 6-phosphogluconate (6PG) acts as an allosteric activator, enhancing enzyme activity by altering rate-limiting steps.
Area of Science:
- Biochemistry
- Enzyme kinetics
- Metabolic pathways
Background:
- 6-phosphogluconate dehydrogenase (6PGDH) is a key enzyme in the pentose phosphate pathway.
- Understanding its catalytic mechanism is crucial for metabolic research.
- Kinetic isotope effects are powerful tools for elucidating enzyme mechanisms.
Purpose of the Study:
- To investigate the reductive carboxylation mechanism of 6-phosphogluconate dehydrogenase (6PGDH) from Candida utilis.
- To determine the role of 6-phosphogluconate (6PG) in regulating 6PGDH activity.
- To characterize the rate-limiting steps of the enzymatic reaction.
Main Methods:
- Utilized kinetic isotope effects (KIEs) with deuterium and tritium isotopes.
- Analyzed the effects of 6-phosphogluconate (6PG) concentration on KIEs.
- Performed kinetic analysis of reductive carboxylation, including K(m) determination.
Main Results:
- An intrinsic isotope effect of 4.9 was observed for proton abstraction from ribulose-5-phosphate (Ru5P).
- The presence of 6PG significantly altered observed isotope effects, indicating a change in rate-limiting steps.
- 6PG at low concentrations decreased the K(m) of Ru5P, suggesting an allosteric activation mechanism.
Conclusions:
- 6PGDH activity is regulated by 6PG, which acts as an allosteric activator.
- The enzyme's catalytic efficiency is optimized when one subunit binds 6PG while another catalyzes the reaction.
- The mechanism involves a shift in rate-limiting steps dependent on 6PG concentration.
Related Concept Videos
01:08Allosteric Regulation
Allosteric regulation of enzymes occurs when the binding of an effector molecule to a site that is different from the active site causes a change in the enzymatic activity. This alternate site is called an allosteric site, and an enzyme can contain more than one of these sites. Allosteric regulation can either be positive or negative, resulting in an increase or decrease in enzyme activity. Most enzymes that display allosteric regulation are metabolic enzymes involved in the degradation or...
01:08Allosteric Regulation
Allosteric regulation of enzymes occurs when the binding of an effector molecule to a site that is different from the active site causes a change in the enzymatic activity. This alternate site is called an allosteric site, and an enzyme can contain more than one of these sites. Allosteric regulation can either be positive or negative, resulting in an increase or decrease in enzyme activity. Most enzymes that display allosteric regulation are metabolic enzymes involved in the degradation or...
01:21Glycolysis: Preparatory Phase
In cellular metabolism (the complete breakdown of glucose to extract energy), glycolysis is the first step. Glycolysis takes place in the cytoplasm of both prokaryotic and eukaryotic cells. Glucose enters heterotrophic cells in two ways. One method is through secondary active transport, where the transport takes place against the glucose concentration gradient. The other mechanism uses a group of integral proteins called GLUT proteins, also known as glucose transporter proteins. These...
01:58Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
01:58Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...
01:58Cooperative Allosteric Transitions
Cooperative allosteric transitions can occur in multimeric proteins, where each subunit of the protein has its own ligand-binding site. When a ligand binds to any of these subunits, it triggers a conformational change that affects the binding sites in the other subunits; this can change the affinity of the other sites for their respective ligands. The ability of the protein to change the shape of its binding site is attributed to the presence of a mix of flexible and stable segments in the...