Related Experiment Video
Updated: Aug 8, 2026
10:20
Evaluation of Photosynthetic Behaviors by Simultaneous Measurements of Leaf Reflectance and Chlorophyll Fluorescence Analyses
Published on: August 9, 2019
Light modulation of phosphofructokinase in pea leaf chloroplasts
B Heuer1, M J Hansen, L E Anderson
1University of Illinois at Chicago Circle, Box 4348, Chicago, Illinois 60680.
Plant Physiology
|June 1, 1982
Summary
Light inactivates key enzymes in pea chloroplasts, including phosphofructokinase. This light effect on phosphofructokinase is similar to dithiothreitol and is inhibited by DCMU, suggesting light regulation of plant carbohydrate metabolism.
Area of Science:
- Plant biochemistry
- Photosynthesis
- Enzyme kinetics
Background:
- Chloroplastic enzymes play crucial roles in plant carbon metabolism.
- Light is a significant environmental factor influencing plant physiological processes.
Purpose of the Study:
- To investigate the effect of light on specific enzymes involved in carbohydrate metabolism in pea chloroplasts.
- To elucidate the mechanism of light inactivation for these enzymes, particularly phosphofructokinase.
Main Methods:
- Enzyme assays were performed on isolated pea chloroplasts under varying light conditions.
- The effects of chemical agents like dithiothreitol, DCMU, arsenite, and sulfite were tested on enzyme activity.
- Kinetic parameters (K(m)) and pH optima for phosphofructokinase were analyzed.
Main Results:
- Four enzymes (phosphofructokinase, phosphorylase, phosphoglucomutase, phosphoglucoisomerase) were found to be light-inactivated in pea chloroplasts.
- Dithiothreitol mimicked the light inactivation effect on phosphofructokinase.
- DCMU, arsenite, and sulfite inhibited the light modulation of phosphofructokinase activity.
- Light inactivation did not alter the K(m) for fructose-6-P or the pH optima of phosphofructokinase.
Conclusions:
- Pea chloroplastic enzymes involved in carbohydrate metabolism are subject to light regulation.
- The mechanism of light inactivation for phosphofructokinase involves redox or sulfhydryl group modification.
- Light modulation of these enzymes likely plays a role in regulating photosynthetic carbon flow.
