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Inactivation of type MM phosphoglycerate mutase by sulfhydryl group reagents during facial embryogenesis
1Department of Histology, University of Gothenburg, Sweden.
Abstract:
Type MM phosphoglycerate mutase from free dissected mandibular processes from embryonic rats was reversibly inactivated by tetrathionate, p-chloromercuribenzoate, and Hg2+. Titration with p-chloromercuribenzoate showed the existence of two sulfhydryl groups per enzyme subunit, the modification of which produced a progressive decline in enzyme activity. The apparent Km values for substrate and cofactor were not affected by tetrathionate treatment. Phosphoglycerate mutase inactivated by tetrathionate and by p-chloromercuribenzoate was unable to form the functionally active phosphorylenzyme when mixed with glycerate-2,3-P2. Glycerate-2,3-P2 protected against tetrathionate but failed to protect against Hg2+ and p-chloromercuribenzoate.
Insights
Sulfhydryl groups in rat mandibular phosphoglycerate mutase are crucial for enzyme activity. Chemical modification of these groups, particularly by mercury (Hg2+) and p-chloromercuribenzoate, inactivates the enzyme.
Area of Science:
- Biochemistry
- Enzymology
- Developmental Biology
Background:
- Phosphoglycerate mutase (PGM) is a key enzyme in glycolysis.
- Understanding PGM's structure-function relationship is vital for metabolic research.
- Embryonic rat mandibular processes offer a specific model for studying PGM.
Purpose of the Study:
- To investigate the role of sulfhydryl groups in Type MM phosphoglycerate mutase activity.
- To determine the effect of specific chemical modifiers on enzyme function.
- To elucidate the mechanism of enzyme inactivation and reactivation.
Main Methods:
- Enzyme isolation from embryonic rat mandibular processes.
- Inactivation studies using tetrathionate, p-chloromercuribenzoate (PCMB), and mercury (Hg2+).
- Enzyme kinetics analysis (Km determination) and titration experiments.
Main Results:
- Type MM phosphoglycerate mutase was inactivated by tetrathionate, PCMB, and Hg2+.
- Two sulfhydryl groups per subunit were identified, critical for activity.
- Inactivated enzyme could not form the active phosphorylenzyme intermediate.
- Glycerate-2,3-P2 protected against tetrathionate but not PCMB or Hg2+.
Conclusions:
- Sulfhydryl groups are essential for phosphoglycerate mutase catalytic activity.
- Different inactivating agents exhibit distinct mechanisms of interaction with the enzyme.
- The findings provide insights into the allosteric regulation and active site of PGM.